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A157968 2^n - 1 (A000225) where n is nonprime number (A141468). 0
0, 1, 15, 63, 127, 255, 511, 1023, 4095, 16383, 32767, 65535, 262143, 1048575, 2097151, 4194303, 16777215, 33554431, 67108863, 134217727, 268435455, 1073741823, 4294967295 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(0) = 0 since 2^0 - 1 = 0 and 0 is nonprime, a(1) = 1 since 2^1 - 1 = 1 and 1 is nonprime, a(2) = 15 since 2^4 - 1 = 15 and 4 is nonprime, ...

LINKS

Table of n, a(n) for n=0..22.

CROSSREFS

A000668

Sequence in context: A066584 A065915 A062965 * A141759 A305616 A104473

Adjacent sequences:  A157965 A157966 A157967 * A157969 A157970 A157971

KEYWORD

nonn

AUTHOR

Jani Melik, Mar 10 2009

STATUS

approved

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Last modified February 20 20:08 EST 2020. Contains 332084 sequences. (Running on oeis4.)