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A287960 Numbers that are the sum of two centered triangular numbers (A005448). 2
2, 5, 8, 11, 14, 20, 23, 29, 32, 35, 38, 41, 47, 50, 56, 62, 65, 68, 74, 77, 83, 86, 89, 92, 95, 104, 110, 113, 116, 119, 128, 131, 137, 140, 146, 149, 155, 167, 170, 173, 176, 182, 185, 194, 197, 200, 203, 209, 212, 218, 221, 230, 236, 239, 245, 251, 254, 263, 266, 272, 275, 278, 281, 284, 293, 299 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..66.

Eric Weisstein's World of Mathematics, Centered Triangular Number

Index entries for sequences related to centered polygonal numbers

FORMULA

8*a(n) = 10+3*A097269(n). - R. J. Mathar, Jul 26 2017

MATHEMATICA

nmax = 300; f[x_] := Sum[x^(3 k (k - 1)/2 + 1), {k, 1, 20}]^2; Exponent[#, x] & /@ List @@ Normal[Series[f[x], {x, 0, nmax}]]

CROSSREFS

Cf. A005448, A020756, A051533, A102795, A286636.

Sequence in context: A070214 A330031 A031210 * A102795 A275603 A275604

Adjacent sequences:  A287957 A287958 A287959 * A287961 A287962 A287963

KEYWORD

nonn

AUTHOR

Ilya Gutkovskiy, Jun 03 2017

STATUS

approved

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Last modified October 20 13:54 EDT 2020. Contains 337904 sequences. (Running on oeis4.)