A216418 Fortunate numbers with increasing multiplicity.

3, 23, 61, 331, 2837, 18169

Offset

1,1

Comments

a(n) appears in A005235 more often than any preceding term.

Is this sequence infinite?

Links

Table of n, a(n) for n=1..6.

Example

3 is the first term of A005235, so a(1) = 3. A005235(5) = A005235(8) = 23, while smaller primes appear only once, so a(2) = 23.

Prog

(PARI) ct(p)=my(pr=1, s); forprime(q=2, p-1, if(!ispseudoprime((pr*=q)+p), next); forprime(r=q+1, p-1, if(ispseudoprime(pr+r), next(2))); s++); s
r=0; forprime(p=2, 2e3, t=ct(p); if(t>r, r=t; print1(p", ")))

Crossrefs

Cf. A005235, A046066.

Sequence in context: A232193 A141047 A196538 * A254626 A362540 A262769

Adjacent sequences: A216415 A216416 A216417 * A216419 A216420 A216421

Keyword

nonn,hard,more

Author

Charles R Greathouse IV, Sep 06 2012

Extensions

a(6) from Charles R Greathouse IV, Sep 17 2012

Status

approved