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A133459 Sums of two nonzero pentagonal pyramidal numbers. 5
2, 7, 12, 19, 24, 36, 41, 46, 58, 76, 80, 81, 93, 115, 127, 132, 144, 150, 166, 197, 201, 202, 214, 236, 252, 271, 289, 294, 306, 322, 328, 363, 392, 406, 411, 414, 423, 445, 480, 484, 531, 551, 556, 568, 576, 590, 601, 625, 676, 693, 727, 732, 744, 746, 766 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Does this sequence ever include a pentagonal pyramidal number? That is, is it ever the case that A002411(i)=A002411(j)+A002411(k) as is often true for triangular pyramidal numbers (tetrahedral numbers) or square pyramidal numbers?

The answer to the above question is yes: A002411(30) + A002411(36) = 13950 + 23976 = 37926 = A002411(42) (see A172425). - Chai Wah Wu, Apr 16 2016

LINKS

Table of n, a(n) for n=1..55.

FORMULA

{A002411(i) + A002411(j) for i, j > 0} = {i^2*(i+1)/2 + j^2*(j+1)/2 for i, j > 0}.

MATHEMATICA

nn = 12; Take[Union@ Map[Total, Tuples[#^2 (# + 1)/2 &@ Range@ nn, 2]], # (# - 1)/2 &[nn - 1]] (* Michael De Vlieger, Apr 16 2016 *)

CROSSREFS

Cf. A002311, A002411, A053721, A172425.

Sequence in context: A297432 A299401 A188039 * A023669 A137401 A309150

Adjacent sequences:  A133456 A133457 A133458 * A133460 A133461 A133462

KEYWORD

nonn

AUTHOR

Jonathan Vos Post, Dec 23 2007

STATUS

approved

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Last modified December 14 09:41 EST 2019. Contains 329979 sequences. (Running on oeis4.)