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A089776 If n mod 10 is 1, 3, 7, or 9, then a(n) = least prime of the form 1 followed by n^r; else a(n) = least prime of the form n^r followed by a 1. In both cases r must be > 1 and a(n) = 0 if no such prime exists. 0
11, 41, 13, 41, 251, 61, 17, 641, 19, 101, 114641, 0, 113, 75295361, 151, 40961, 1289, 181, 1361, 4001, 11025506433613486607375777617584133309366191904729927960524981845743709132117581, 1368800680154120519681, 1907846434775996175406740561329, 241, 251, 6761, 127, 281, 1500246412961, 9001, 131 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subsidiary sequence: 3 more sequences can be obtained by replacing 1 by 3,7 and 9.

LINKS

Table of n, a(n) for n=1..31.

FORMULA

If n is divisible by 2 or 5, a(n) = A088622(n); otherwise a(n) = A088623(n). - David Wasserman, Oct 12 2005

EXAMPLE

a(12) = 0 because 1+10*12^r is always divisible by 11.

a(32) = 0 because 1+10*32^r is divisible by 3 if r is odd and by 11 if r is even.

CROSSREFS

Cf. A088622, A088623.

Sequence in context: A225919 A064768 A135719 * A073626 A065144 A089348

Adjacent sequences:  A089773 A089774 A089775 * A089777 A089778 A089779

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Nov 24 2003

EXTENSIONS

More terms from David Wasserman, Oct 12 2005

STATUS

approved

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Last modified March 31 19:37 EDT 2020. Contains 333151 sequences. (Running on oeis4.)