which authors published works under more than one name (not just a pen
name but, like Dr. Seuss, had two or more names that were used)

Hi killermunchkin,

Here are the authors with more than one pen name. I'll list the real
name first and then their pseudonyms.

Roderic Jeffries: Jeffrey Ashford - Peter Alding
Mabel E. Allan: Jean Estoril - Pricilla Haggon
Jean Bowden: Jennifer Bland - Avon Curry -  Tessa Barclay
W.E.Butterworth: Alex Balwin - W.E.B. Griffin
Anthony C. Lewing: Rowena Carter - Mark Bannerman
Dianne Day: Madelyn Sanders - Diana Bane
Marion Chesney: - Helen Crampton - Ann Fairfax - Jennie Tremaine -
Charlotte Ward - M.C. Beaton
Anthony Berkeley: A B Cox - Frances Iles
Elizabeth Linington: Lesley Egan - Egan O'Neill - Dell Shannon - Anne
Blaisdell
Claire Dawson: Edna Francis - Edna Jebison - Edna Anne Jones - Kim
Bolton
Marjorie Eccles: Jennifer Hyde - Judith Bordill
Otto R. Braun: Rolf Otten Orb - Pitt Strong - Eric G. Taylor
Andrew Gardner: Andrew Harrell - Roy Burns
Sara Woods: Mary Challis - Margaret Leek - Anne Burton
Herbert Harris: Michael Moore - Jerry Regan - Frank Bury
Evan Hunter: Richard Marsten - Ed McBain - Hunt Collins - Curt Cannon
Eleanor Hibbert: Victoria Holt - Kathleen Kellow - Jean Plaidy -
Ellalice Tate - Philippa Carr
Christopher Samuel Youd: Hilary Ford - Peter Graaf - Samuel Youd -
John Christopher
P. C. Doherty: Paul Harding - Michael Clynes
Bob Mayer: Bob McGuire - Robert Doherty
Bill Pronzini: Jack Saxon - Jack Foxx
Lucy Beatrice Malleson: Anne Meredith - J. Kilmeny Keity - Anthony
Gilbert
Orania Papazoglou: Ann Paris - Jane Haddam
Nicholas Yermakov: J.D. Masters - S.L. Hunter - Simon Hawke
Al Lacy: Hank Mitchum - Bill Reno - Morgan Hill
Reginald Hill: Dick Morland - Patrick Ruell - Charles Underhill
Dean R. Koontz: David Axton - Brian Coffey - Deanna Dwyer - K.R. Dwyer
- John Hill - Leigh Nichols - Anthony North - Richard Paige - Owen
West
Kenneth Millar: John Macdonald - Ross Macdonald - John Ross Macdonald
Lee Martin: Martha G. Webb - Anne Wingate
Barbara Mertz: Elizabeth Peters - Barbara Michaels
Sheri C. Tepper:  B.J. Oliphant - A.J. Orde
Hugh C. Rae: James Albany - Jessica Stirling
Elly Wilder: J.D. Robb - Nora Roberts

Search terms used:
authors with pseudonyms

I hope you found this helpful.

Best regards,
rainbow-ga

Don't forget Frank Richards, the most prolific author of all time.

Hector Hugh Munro: H.H. Munro - Saki

Lawrence Block: Paul Kavenaugh - Chip Harrison

John Dickson Carr: Carter Dixon - Carr Dickson

Eleanor Alice Hibbert: 5 names above + Elbur Ford & Eleanor Burford 

Dennis Lynds: Maxwell Grant - William Arden - Mark Sadler - John Crowe
- Nick Carter - Michael Collins

Michael [Angelo] Avallone, Jr.: Nick Carter - Troy Conway - Priscilla
Dalton - Marl Dane - Jean-Anne de Pre - Dora Highland - Stuart Jason -
Steve Michaels -  Dorothea Nile - Edwina Noone - Vance Stanton -
Sidney Stuart - Max Walker - Lee Davis Willoughby