A136402 Prime Wedderburn-Etherington numbers.

2, 3, 11, 23, 983, 2179, 24631, 3626149, 253450711, 596572387, 4958179972866730572551, 17950473826186485808766524097, 17690812163571687513245304152178763697755384812733, 9852801774222802457119814738073136914072348071335480633169417277909155746150705781482843

Offset

1,1

Comments

Corresponding indices are 4, 5, 7, 8, 13, 14, 17, 23, 28, 29, 63, 80, 134, 233, 534, 732, 1963, 3896, 7792, 7987, 8312, ... with no more up to 2*10^4. - Charles R Greathouse IV, Mar 23 2014

Next index which produces a prime is 48979. - Robert G. Wilson v, May 21 2014

Links

Table of n, a(n) for n=1..14.

Mathematica

a[n_?OddQ] := a[n] = Sum[a[k]*a[n - k], {k, 1, (n - 1)/2}]; a[n_?EvenQ] := a[n] = Sum[a[k]*a[n - k], {k, 1, n/2 - 1}] + (1/2)*a[n/2]*(1 + a[n/2]); a[0] = 0; a[1] = 1; Select[a@# & /@ Range@ 300, PrimeQ@# &] (* Robert G. Wilson v, May 20 2014, after Jean-François Alcover in A001190 *)

Crossrefs

Cf. A001190.

Sequence in context: A363141 A374914 A065849 * A137811 A041955 A239445

Adjacent sequences: A136399 A136400 A136401 * A136403 A136404 A136405

Keyword

nonn

Author

Charles R Greathouse IV, Mar 30 2008

Status

approved