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A065585 Smallest prime beginning with exactly n 2's. 5
3, 2, 223, 2221, 22229, 2222203, 22222253, 22222223, 222222227, 22222222273, 22222222223, 2222222222243, 22222222222201, 22222222222229, 222222222222227, 222222222222222043, 222222222222222281, 222222222222222221, 22222222222222222253, 222222222222222222277 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

M. F. Hasler, Table of n, a(n) for n = 0..200

MATHEMATICA

Do[a = Table[2, {n}]; k = 0; While[b = FromDigits[ Join[a, IntegerDigits[k] ]]; First[ IntegerDigits[k]] == 2 || !PrimeQ[b], k++ ]; Print[b], {n, 1, 17} ]

PROG

(PARI) A065585(n)={n=10^n\9*2; n>2&for(d=1, 9e9, n*=10; for(t=1, 10^d-1, t\10^(d-1)==2 & t+= 10^(d-1)+(t>2); ispseudoprime(n+t) & return(n+t))); 2+!n} \\ - M. F. Hasler, Oct 17 2012

CROSSREFS

Cf. A037057, A065584 - A065592.

A068103 is a lower bound, but most often equality holds. - M. F. Hasler, Oct 17 2012

Sequence in context: A187825 A297532 A037057 * A139737 A036113 A226840

Adjacent sequences:  A065582 A065583 A065584 * A065586 A065587 A065588

KEYWORD

nonn,base

AUTHOR

Robert G. Wilson v, Nov 28 2001

EXTENSIONS

Corrected by Don Reble, Jan 17 2007

STATUS

approved

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Last modified January 19 03:54 EST 2020. Contains 331031 sequences. (Running on oeis4.)