A244624 Consider the number of lines in the Pratt certificate for the n-th prime (A037202). This sequence shows where 2n first occurs.

1, 2, 4, 9, 14, 34, 61, 120, 215, 690, 1144, 2584, 5626, 13709, 31275, 63461, 145767, 340332, 649190, 1703684, 4218462, 10675070, 22892978

Offset: 0

Author

Joerg Arndt and Robert G. Wilson v, Jul 02 2014

Keywords

• nonn
• more

Comments

See comment section of A037202.

a(n) ~ 2*a(n-1).

Crossrefs

Cf. A037202, A037231.

Programs

Mathematica

a[1] = 1; a[n_] := a[n] = 1 + Plus @@ (a@ PrimePi@# & /@ First /@ FactorInteger[ Prime@ n - 1]); k = 1; t = Table[0, {1000}]; While[k < 1000000000000001, If[a@ k < 1001 && t[[a[k]/2]] == 0, t[[a[k]/2]] = k; Print[{a@k, k}]]; k++]; t

Formula

Also PrimePi( A037231 ).