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A280089 a(n) = 4 * n^3 - 3 * n + 1. 2
1, 2, 27, 100, 245, 486, 847, 1352, 2025, 2890, 3971, 5292, 6877, 8750, 10935, 13456, 16337, 19602, 23275, 27380, 31941, 36982, 42527, 48600, 55225, 62426, 70227, 78652, 87725, 97470, 107911, 119072, 130977, 143650, 157115, 171396, 186517, 202502, 219375 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Daniel Suteu, Table of n, a(n) for n = 0..750

FORMULA

a(n) = (2n - 1)^2 * (n + 1).

Prod_{k >= 1}(A033430(k) / a(k)) = Pi.

MATHEMATICA

Table[4n^3 - 3n + 1, {n, 0, 39}] (* Alonso del Arte, Dec 25 2016 *)

PROG

(PARI) a(n) = (2*n-1)^2 * (n+1).

CROSSREFS

Cf. A033430.

Sequence in context: A206585 A046735 A038625 * A041801 A166942 A119351

Adjacent sequences:  A280086 A280087 A280088 * A280090 A280091 A280092

KEYWORD

nonn,easy

AUTHOR

Daniel Suteu, Dec 25 2016

STATUS

approved

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Last modified May 28 02:51 EDT 2017. Contains 287211 sequences.