A098168 Prime index j such that prime(j) = the n-th fortunate number, A005235(n).

2, 3, 4, 6, 9, 7, 8, 9, 12, 18, 19, 18, 20, 15, 28, 17, 18, 29, 24, 27, 22, 36, 45, 26, 27, 51, 48, 31, 48, 43, 38, 50, 117, 52, 37, 39, 85, 52, 46, 43, 46, 76, 51, 133, 65, 137, 111, 65, 76, 62, 86, 67, 61, 59, 58, 79, 63, 67, 75, 94, 67, 64, 78, 67, 71, 81, 82, 153, 101, 221

Offset

1,1

Links

Table of n, a(n) for n=1..70.

Antonín Čejchan, Michal Křížek, and Lawrence Somer, On Remarkable Properties of Primes Near Factorials and Primorials, Journal of Integer Sequences, Vol. 25 (2022), Article 22.1.4.

Mathematica

NextPrime[n_Integer] := Block[{k}, k = n + 1; While[ !PrimeQ[k], k++ ]; k]; Fortunate[n_Integer] := Block[{p = Product[Prime[i], {i, 1, n}] + 1, q}, q = NextPrime[p]; q - p + 1]; Table[ PrimePi[ Fortunate[n]], {n, 70}] (* Robert G. Wilson v, Sep 04 2004 *)

Crossrefs

Cf. A005235, A055211, A098166, A098167.

Sequence in context: A363995 A141396 A159849 * A306441 A370981 A207831

Adjacent sequences: A098165 A098166 A098167 * A098169 A098170 A098171

Keyword

nonn

Author

Pierre CAMI, Aug 30 2004

Extensions

More terms from Robert G. Wilson v, Sep 04 2004

Better definition from R. J. Mathar, Oct 28 2007

Status

approved