A007546 Number of steps to compute n-th prime in PRIMEGAME (fast version).

19, 69, 280, 707, 2363, 3876, 8068, 11319, 19201, 36866, 45551, 75224, 101112, 117831, 152025, 215384, 293375, 327020, 428553, 507519, 555694, 700063, 808331, 989526, 1273490, 1434366, 1530213, 1710923, 1818254, 2019962, 2833089, 3104685, 3546320, 3720785

Offset: 1

Author

N. J. A. Sloane

Keywords

• easy
• nonn
• nice

References

• D. Olivastro, Ancient Puzzles. Bantam Books, NY, 1993, p. 21.
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..5000
• J. H. Conway, FRACTRAN: a simple universal programming language for arithmetic, in T. M. Cover and Gopinath, eds., Open Problems in Communication and Computation, Springer, NY 1987, pp. 4-26.
• R. K. Guy, Conway's prime producing machine, Math. Mag. 56 (1983), no. 1, 26-33.
• Wikipedia, Conway's PRIMEGAME

Crossrefs

Cf. A007542, A007547.

Programs

Maple

with(numtheory): f:= proc(n) local l, b, d; l:= sort([divisors (n)[]]); b:= l[nops(l)-1]; n-1 +(6*n+2)*(n-b) +2*add(floor(n/d), d=b..n-1) end: a:= proc(n) option remember; `if`(n=1, f(2), a(n-1) +add(f(i), i=ithprime(n-1)+1..ithprime(n))) end: seq(a(n), n=1..40); # Alois P. Heinz, Aug 12 2009

Mathematica

f[n_] := Module[{l, b, d}, l = Divisors [n]; b = l[[-2]]; n-1 + (6*n+2)*(n-b) + 2*Sum[Floor[n/d], {d, b, n-1}]]; a[n_] := a[n] = If[n == 1, f[2], a[n-1] + Sum[f[i], {i, Prime[n-1]+1, Prime[n]}]]; Table[a[n], {n, 1, 32}] (* Jean-François Alcover, Oct 04 2013, translated from Alois P. Heinz's Maple program *)

Extensions

More terms from Alois P. Heinz, Aug 12 2009