A038532 Primes that are concatenations of k-th composite and k-th prime.

97, 1213, 2137, 2861, 3067, 3271, 3373, 3583, 48131, 55163, 56167, 57173, 62191, 70229, 86293, 90313, 93337, 96353, 99367, 104383, 105389, 106397, 108401, 117443, 123479, 126499, 129509, 132523, 133541, 138569, 143593, 145601

Offset: 1

Author

Vasiliy Danilov (danilovv(AT)usa.net), Jul 14 1998

Keywords

• nonn
• base

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A038531.

Programs

Mathematica

nn=250;Module[{prs=Prime[Range[nn]],comps,concats},comps=Take[Complement[ Range[2,Prime[nn]+1], prs],nn];concats=FromDigits[Flatten[ IntegerDigits/@#]]&/@ Thread[{comps,prs}];Select[concats,PrimeQ]] (* Harvey P. Dale, Apr 27 2012 *)

Extensions

Edited by Charles R Greathouse IV, Apr 23 2010