A133661 No sum of 2 or more terms equals a prime, terms alternate parity and there are no primes in the list.

1, 8, 25, 86, 209, 472, 25719, 238350, 41931245, 14426603100

Offset

1,2

Comments

a(10) > 263811880. - Robert G. Wilson v, Jan 01 2008

Links

Table of n, a(n) for n=1..10.

Example

25 is a term, because 25 is odd (previous term was even), 25 is composite and 25+1, 25+8 and 25+8+1 are all composite.

Mathematica

(* first do *) Needs["Combinatorica`"] (* then *) lst = {1, 8}; g[k_] := Block[{j = 1, l = 2^Length@lst}, While[j < l && !PrimeQ[Plus @@ NthSubset[j, lst] + k], j++ ]; If[j == l, False, True]]; f[n_] := Block[{k = lst[[ -1]] + 1}, While[PrimeQ@k || g[k] == True, k++; k++ ]; AppendTo[lst, k]; k]; Do[ Print@ f@ n, {n, 10}] (* Robert G. Wilson v, Jan 01 2008 *)

Crossrefs

Cf. A052349, A133660.

Sequence in context: A035073 A041120 A042637 * A229443 A335769 A139026

Adjacent sequences: A133658 A133659 A133660 * A133662 A133663 A133664

Keyword

more,nonn

Author

Randy L. Ekl, Dec 28 2007

Extensions

a(9) from Robert G. Wilson v, Jan 01 2008

a(10) from Donovan Johnson, Feb 15 2008

Status

approved