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 A121405 Numbers that are not the sum of distinct pentagonal numbers (A000326). 4
 2, 3, 4, 7, 8, 9, 10, 11, 14, 15, 16, 19, 20, 21, 24, 25, 26, 29, 30, 31, 32, 33, 37, 38, 42, 43, 44, 45, 46, 49, 50, 54, 55, 59, 60, 61, 65, 66, 67, 72, 77, 80, 81, 84, 89, 94, 95, 96, 100, 101, 102, 107, 112, 116, 124, 136, 137, 141, 142, 147, 159 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For sums of distinct generalized pentagonal numbers (A001318), only 4 and 11 are not representable. LINKS MATHEMATICA nn=50; a=Table[n(3n-1)/2, {n, nn}]; t=Rest[CoefficientList[Series[Product[(1+x^a[[k]]), {k, nn}], {x, 0, a[[ -1]]}], x]]; Flatten[Position[t, 0]] CROSSREFS Cf. A025524 (number of numbers not the sum of distinct n-th-order polygonal numbers) Cf. A007419 (largest number not the sum of distinct n-th-order polygonal numbers) Cf. A053614, A001422 (corresponding sequences for triangular and square numbers) Sequence in context: A037466 A285405 A305441 * A330217 A231003 A171551 Adjacent sequences:  A121402 A121403 A121404 * A121406 A121407 A121408 KEYWORD fini,nonn AUTHOR T. D. Noe, Jul 28 2006 STATUS approved

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Last modified September 28 01:27 EDT 2021. Contains 347698 sequences. (Running on oeis4.)