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 A061337 Smallest number of distinct triangular numbers which sum to n (or -1 if not possible). 1
 0, 1, -1, 1, 2, -1, 1, 2, -1, 2, 1, 2, -1, 2, 3, 1, 2, 3, 2, 3, 4, 1, 2, -1, 2, 2, 3, 2, 1, 2, 3, 2, 3, -1, 2, 3, 1, 2, 2, 2, 3, 3, 2, 2, 3, 1, 2, 3, 2, 2, 3, 2, 3, 3, 3, 1, 2, 2, 2, 3, 2, 2, 3, 3, 2, 2, 1, 2, 3, 2, 2, 3, 2, 2, 3, 3, 2, 3, 1, 2, 3, 2, 3, 2, 2, 3, 3, 2, 2, 3, 3, 1, 2, 2, 2, 3, 3, 2, 3, 2, 2, 2, 2, 3, 3, 1, 2, 3, 2, 3, 3, 2, 2, 3, 2, 2, 3, 3, 3, 2, 1, 2, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS 20 is the only case where n>3. LINKS EXAMPLE a(20)=4 since 20=1+3+6+10, a(21)=1 since 21 is triangular, a(22)=2 since 22=1+21, a(23)=-1 since no combination of distinct triangular numbers sum to 23. CROSSREFS Cf. A000217, A002243, A053614, A061208, A061336. Sequence in context: A071709 A131406 A029440 * A253051 A103684 A105103 Adjacent sequences:  A061334 A061335 A061336 * A061338 A061339 A061340 KEYWORD sign AUTHOR Henry Bottomley, Apr 25 2001 STATUS approved

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Last modified May 5 18:13 EDT 2021. Contains 343572 sequences. (Running on oeis4.)