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A138965 Least prime factor of concatenation of first n odd numbers. 2
1, 13, 3, 23, 37, 3, 11617, 5, 3, 135791113151719, 29, 3, 5, 11, 3, 135791113151719212325272931, 17, 3, 7, 13, 3, 131, 5, 3, 11, 25471443030907588399109, 3, 5, 7, 3, 181, 41, 3, 135791113151719212325272931333537394143454749515355575961636567, 19, 3, 40351, 5, 3, 7, 11, 3, 5, 57041, 3, 351269, 11, 3, 135791113151719212325272931333537394143454749515355575961636567697173757779818385878991939597 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Sean A. Irvine, Table of n, a(n) for n = 1..300

F. Smarandache, Sequences of numbers involved in unsolved problems, arXiv:math/0604019

FORMULA

A138965(n) = A020639(A019519(n)) (= 3 if n = 0 (mod 3)).

PROG

(PARI) t=1; for( n=2, 99, print1( factor( eval( t=Str( t, 2*n-1 )))[1, 1], ", "))

CROSSREFS

Cf. A019519, A046036, A048847; A109837, A104644.

Sequence in context: A213538 A264971 A107806 * A317313 A170922 A005602

Adjacent sequences:  A138962 A138963 A138964 * A138966 A138967 A138968

KEYWORD

base,nonn

AUTHOR

M. F. Hasler, Apr 14 2008

STATUS

approved

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Last modified July 20 01:17 EDT 2019. Contains 325168 sequences. (Running on oeis4.)