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A244624 Consider the number of lines in the Pratt certificate for the n-th prime (A037202). This sequence shows where 2n first occurs. 0
1, 2, 4, 9, 14, 34, 61, 120, 215, 690, 1144, 2584, 5626, 13709, 31275, 63461, 145767, 340332, 649190, 1703684, 4218462, 10675070, 22892978 (list; graph; refs; listen; history; text; internal format)
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: A227377 A173407 A113862 * A036277 A042960 A266596

Adjacent sequences:  A244621 A244622 A244623 * A244625 A244626 A244627

KEYWORD

nonn,more

AUTHOR

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

STATUS

approved

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Last modified September 16 02:16 EDT 2019. Contains 327088 sequences. (Running on oeis4.)