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A078671
Number of times the n-th prime appears among the decimal digits of 2^(2^n) + 1, the Fermat numbers.
0
0, 0, 1, 1, 0, 0, 1, 1, 2, 4, 9, 14, 21, 46, 112, 204, 374, 809, 1586, 3237, 6385, 12539, 25637, 50603, 100891, 20382, 40281, 81405, 161718, 323703, 645928
OFFSET
1,9
COMMENTS
Conjectures: Is a(n) monotonically increasing for n > 4? Does lim{n->inf} a(n)/a(n+1) = 0.5? - Ryan Propper, Jan 04 2008
EXAMPLE
a(4)=1 because the 4th prime 7 appears once in 2^2^4 + 1 = 65537.
PROG
(PARI) {mcf(d, n)=my(c=0, m=10^#digits(d)); while(n>0, if(n%m==d, c++); n\=10; ); c }
a(n) = {mcf(prime(n), (2^2^n+1))}
CROSSREFS
Cf. A000215.
Sequence in context: A190553 A270532 A281407 * A119637 A169762 A291465
KEYWORD
base,more,nonn
AUTHOR
Jason Earls, Dec 16 2002
EXTENSIONS
More terms from Ryan Propper, Jan 04 2008
a(24)-a(26) from Donovan Johnson, Nov 17 2008
Correction of a(26). a(27)-a(31) from Robert Gerbicz, Nov 24 2010
STATUS
approved