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(P(p)-1)/2/p^2 where p runs through the odd primes different from 5 and P(k) is the k-th central pentanomial coefficient (A005191).
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%I #9 Mar 31 2012 13:48:24

%S 1,83,16907,279021,89444018,1695011087,658067703933,5768410509553937,

%T 122108313460051500,1226978854222034501448,593538703869555995238872,

%U 13175226571428140572866093,6594852118968926152838341468

%N (P(p)-1)/2/p^2 where p runs through the odd primes different from 5 and P(k) is the k-th central pentanomial coefficient (A005191).

%H M. F. Hasler, <a href="/A087189/b087189.txt">Table of n, a(n) for n = 1..100</a>

%o (PARI) A087189(n) = local(p=prime(n+2-(n==1))); (A005191(p)-1)/2/p^2 \\ - M. F. Hasler

%K nonn

%O 1,2

%A _Benoit Cloitre_, Oct 19 2003

%E Corrected and extended by _M. F. Hasler_, Jul 23 2007