A375545 Indices of the Sylvester primes (A375543) in the primes (A000040).

1, 2, 4, 14, 6, 34, 101, 111, 174, 42, 300, 21, 340, 3238, 1652, 2049, 3345, 5354, 6676, 7322, 12037, 30205, 51733, 7357, 99091, 167580, 2967, 15042, 2354, 193, 25884, 126695, 232179, 234477, 11370, 37546, 176867, 28678, 3270, 578, 84666, 966, 284, 349823, 2645

Offset: 1

Author

Peter Luschny, Sep 05 2024

Keywords

• nonn

Examples

			a(7) = 101 because A375543(7) = 547 = A000040(101).
		

Crossrefs

Cf. A000040, A000720, A375543.

Programs

Mathematica

Module[{nmax = 20, a = {}, p = 1, f}, Do[p *= p + 1; f = 2; While[MemberQ[a, f] || !Divisible[p, f], f = NextPrime[f]]; AppendTo[a, f], nmax]; PrimePi[a]] (* Paolo Xausa, Sep 09 2024 *)

Formula

a(n) = A000720(A375543(n)).

Extensions

More terms from Jinyuan Wang, Jul 25 2025