0,1

a(4) = 1551551 because its digital product is 5^4.

NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; a = Table[0, {18}]; p = 2; Do[q = Log[5, Times @@ IntegerDigits[p]]; If[q != 0 && IntegerQ[q] && a[[q]] == 0, a[[q]] = p; Print[q, " = ", p]]; p = NextPrim[p], {n, 1, 10^9}]

For a(13); a = Map[ FromDigits, Permutations[{1, 1, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5}]]; Min[ Select[a, PrimeQ[ # ] &]]

Cf. A089365, A088653, A091465, A090841, A089298.

Sequence in context: A120831 A038319 A002547 this_sequence A080501 A122098 A115943

Adjacent sequences: A090837 A090838 A090839 this_sequence A090841 A090842 A090843

base,nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 09 2003