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

0,2

Comments

See comment section of A037202.

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

Links

Table of n, a(n) for n=0..22.

Formula

Also PrimePi( A037231 ).

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

Crossrefs

Cf. A037202, A037231.

Sequence in context: A341959 A173407 A113862 * A343592 A036277 A042960

Adjacent sequences: A244621 A244622 A244623 * A244625 A244626 A244627

Keyword

nonn,more

Author

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

Status

approved