A079154 Numbers k such that reverse(A004154(k)) - 1 is prime.

3, 4, 12, 30, 33, 1406

Offset: 1

Author

Jason Earls and Robert G. Wilson v, Dec 27 2002

Keywords

• base
• more
• nonn

Comments

The values corresponding to a(1)-a(6) have been certified prime with Primo. a(7) > 15000. - Giovanni Resta, Feb 20 2013

a(7) > 40000. - Michael S. Branicky, Jan 05 2025

Crossrefs

Cf. A078305, A004154.

Programs

Mathematica

f[n_] := n!/10^Sum[Floor[n/5^k], {k, 1, Log[10, n] + 1}]; Do[ If[ PrimeQ[ FromDigits[ Reverse[ IntegerDigits[ f[n]]]] - 1], Print[n]], {n, 1, 800}]

Extensions

a(6) from Giovanni Resta, Feb 20 2013