A014795 - OEIS

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A014795

Squares of odd tetrahedral numbers.

1, 1225, 27225, 207025, 938961, 3136441, 8555625, 20205025, 42837025, 83521321, 152300281, 262926225, 433680625, 688275225, 1056835081, 1576963521, 2294889025, 3266694025, 4559625625, 6253488241, 8442118161, 11234940025, 14758605225, 19158712225, 24601608801

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..24.

Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).

FORMULA

From Amiram Eldar, Mar 07 2022: (Start)

a(n) = A015219(n)^2 = ((4*n+1)*(4*n+2)*(4*n+3)/6)^2.

Sum_{n>=0} 1/a(n) = 9*Pi*(Pi-3)/4. (End)

MATHEMATICA

Table[((4*n+1)*(4*n+2)*(4*n+3)/6)^2, {n, 0, 40}] (* Amiram Eldar, Mar 07 2022 *)