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A025702 Index of 4^n within sequence of numbers of form 4^i*5^j. 2
1, 2, 4, 7, 11, 16, 22, 29, 36, 44, 53, 63, 74, 86, 99, 112, 126, 141, 157, 174, 192, 211, 230, 250, 271, 293, 316, 340, 365, 390, 416, 443, 471, 500, 530, 561, 593, 625, 658, 692, 727, 763, 800, 838, 876, 915, 955, 996, 1038, 1081, 1125, 1169, 1214, 1260, 1307, 1355 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 0..10000

PROG

(PARI) a(n)=my(N=1); n+1+sum(i=1, n, logint(N<<=2, 5)); \\ Charles R Greathouse IV, Jan 11 2018

(PARI) first(n)=my(s, N=1/4); vector(n+1, i, s+=logint(N<<=2, 5)+1) \\ Charles R Greathouse IV, Jan 11 2018

CROSSREFS

Differs from A025717 at a(65).

Sequence in context: A024224 A025727 A319159 * A025717 A025726 A070280

Adjacent sequences:  A025699 A025700 A025701 * A025703 A025704 A025705

KEYWORD

nonn,easy

AUTHOR

David W. Wilson

EXTENSIONS

Offset corrected by Charles R Greathouse IV, Jan 11 2018

STATUS

approved

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Last modified April 3 00:26 EDT 2020. Contains 333194 sequences. (Running on oeis4.)