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(A000670(2*p - 1) - 1)/(6*p) where p runs through the primes.
1

%I #14 Sep 10 2019 05:21:37

%S 1,30,236242,12544246390,1229164015128849604270,

%T 1367914941518920202892096130,

%U 10989801394147610473210727542088302770490,67520322268089344459189867921056960354422886750

%N (A000670(2*p - 1) - 1)/(6*p) where p runs through the primes.

%H Amiram Eldar, <a href="/A079601/b079601.txt">Table of n, a(n) for n = 1..47</a>

%t f[0]=1; f[n_] := f[n] = Sum[Binomial[n, k] * f[n - k], {k, 1, n}]; r[p_] := (f[2 p - 1] - 1)/(6 p); r /@ Select[Range[20], PrimeQ] (* _Amiram Eldar_, Sep 10 2019 *)

%Y Cf. A000670.

%K nonn

%O 1,2

%A _Benoit Cloitre_, Jan 28 2003

%E Definition corrected by _Eric Rowland_, Jun 23 2017