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A063384 a(1) = 7, a(n) = concatenation of two closest factors of a(n-1) whose product equals a(n-1) or if a(n-1) is a prime then the concatenation of 1 and a(n-1). 0
7, 17, 117, 913, 1183, 1391, 13107, 51257, 151257, 381397, 577661, 4911789, 29116879, 112646989, 536920981, 1928258999, 11928258999, 25227472837, 46275452231, 212892173679, 370964057893, 1859199550327, 5593332415439 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..23.

MATHEMATICA

f[ n_Integer ] := (d = Divisors[ n ]; l = Length[ d ]; If[ EvenQ[ l ], ToExpression[ ToString[ d[[ l/2 ] ]] <> ToString[ d[[ l/2 + 1 ]] ]], ToExpression[ ToString[ d[[ l/2 + .5 ] ]] <> ToString[ d[[ l/2 + .5 ] ]] ]] ); NestList[ f, 7, 25 ]

CROSSREFS

Cf. A003681, A062094 and A062095.

Sequence in context: A205989 A262474 A284416 * A165246 A266382 A118108

Adjacent sequences:  A063381 A063382 A063383 * A063385 A063386 A063387

KEYWORD

base,nonn

AUTHOR

Robert G. Wilson v, Aug 09 2001

STATUS

approved

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Last modified July 12 10:20 EDT 2020. Contains 335657 sequences. (Running on oeis4.)