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Search: id:A121405
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| A121405 |
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Numbers that are not the sum of distinct pentagonal numbers (A000326). |
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+0
1
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| 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; listen)
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OFFSET
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1,1
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COMMENT
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For sums of distinct generalized pentagonal numbers (A001318), only 4 and 11 are not representable.
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MATHEMATICA
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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]]
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CROSSREFS
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Cf. A053614 (numbers not the sum of distinct triangular numbers), A001422 (numbers not the sum of distinct squares), A007419 (largest number not the sum of distinct n-gonal numbers).
Sequence in context: A047337 A039049 A037466 this_sequence A096199 A104576 A031477
Adjacent sequences: A121402 A121403 A121404 this_sequence A121406 A121407 A121408
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KEYWORD
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fini,nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Jul 28 2006
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