A078190 Primes of the form A004154(n) - 1.

5, 23, 11, 71, 503, 62270207, 871782911, 121645100408831, 243290200817663, 304888344611713860501503, 137637530912263450463159795815809023

Offset: 1

Author

Cino Hilliard, Dec 23 2002

Keywords

• nonn

Comments

More precisely, scan A004154, subtract 1 and record the answer if it is a prime. The sequence is not monotonic.

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..17

Crossrefs

Cf. A004154, A078154, A078203, A078305.

Programs

Maple

A004154 := proc(n) option remember ; local m ; if n <= 1 then RETURN(1) ; else m := A004154(n-1)*n ; while m mod 10 = 0 do m := m /10 ; end ; RETURN(m) ; fi ; end: n := 1 ; while true do f := A004154(n) : if isprime(f-1) then printf("%d, ",f-1) ; fi ; n := n+1 : od : # R. J. Mathar, Feb 27 2007

PARI

v=[];for(n=1,500,if(ispseudoprime(t=n!/10^valuation(n!,5)-1),v=concat(v,t))); v \\ Charles R Greathouse IV, Feb 14 2011

Extensions

More terms from R. J. Mathar, Feb 27 2007