A055732 - OEIS

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A055732

Number of primes <= 7^n.

0, 4, 15, 68, 357, 1939, 11098, 65685, 397764, 2453911, 15353323, 97163605, 620646217, 3995149838, 25885182840, 168650876819, 1104127111380, 7259025764932, 47901523494261, 317140339436292, 2105877503513609, 14020561559878216, 93570332318306847, 625829902867176558, 4194084944321575624, 28158446635057280702, 189368274899202732322

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OFFSET

0,2

LINKS

David Baugh, Table of n, a(n) for n = 0..30 (terms n = 27..30 found using Kim Walisch's primecount program)

Index entries for sequences related to numbers of primes in various ranges

FORMULA

a(n) = A000720(A000420(n)). - Michel Marcus, Aug 25 2014

MATHEMATICA

Table[PrimePi[7^n], {n, 0, 16}]

PROG

(PARI) a(n) = primepi(7^n); \\ Michel Marcus, Aug 25 2014