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A083215 a(n) = 1 + Sum(prime(i)*(2*i-1): 1<=i<=n). 1

%I

%S 3,12,37,86,185,328,549,834,1225,1776,2427,3278,4303,5464,6827,8470,

%T 10417,12552,15031,17800,20793,24190,27925,32108,36861,42012,47471,

%U 53356,59569,66236,73983,82236,91141,100454,110735,121456,132917

%N a(n) = 1 + Sum(prime(i)*(2*i-1): 1<=i<=n).

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/FigurateNumber.html">Figurate Number.</a>

%t nxt[{n_, a_}] := {n + 1, a + Prime[n + 1] (2 n + 1)}; NestList[nxt,{1,2},50][[All,2]]+1 (* _Harvey P. Dale_, Jul 05 2018 *)

%Y Cf. A002412.

%Y Equals 1 + A316322(n).

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Jun 01 2003

%E Definition corrected by _Harvey P. Dale_, Jul 03 2018

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Last modified August 11 04:03 EDT 2020. Contains 336421 sequences. (Running on oeis4.)