A039790 Prime numbers prefixed with a '1'.

12, 13, 15, 17, 111, 113, 117, 119, 123, 129, 131, 137, 141, 143, 147, 153, 159, 161, 167, 171, 173, 179, 183, 189, 197, 1101, 1103, 1107, 1109, 1113, 1127, 1131, 1137, 1139, 1149, 1151, 1157, 1163, 1167, 1173, 1179, 1181, 1191, 1193, 1197, 1199, 1211

Offset: 1

Author

Kevin N. Stone (kevin.stone(AT)brainbashers.com)

Keywords

• nonn
• base
• dumb

Comments

Replace every prime by the concatenation of its divisors. [Lekraj Beedassy, May 29 2009]

Links

• David F. Marrs, Table of n, a(n) for n = 1..10000
• Kevin N. Stone, What number comes next in this sequence, BrainBashers [Archived copy at the Wayback Machine].

Crossrefs

Cf. A000040, A037278, A289866 (terms which are prime).

Programs

Mathematica

Array[10^Floor[1 + Log10[#]] + # &@ Prime[#] &, 47] (* Michael De Vlieger, Apr 05 2021 *)

PARI

a(n) = eval(concat(Str(1), Str(prime(n)))) \\ Felix Fröhlich, Apr 05 2021

Formula

a(n) = A037278(A000040(n)). [Lekraj Beedassy, May 29 2009]