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A063423
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a(1) = 9, 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).
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0
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9, 33, 311, 1311, 2357, 12357, 91373, 191373, 273701, 594639, 966071, 3792549, 7714919, 18474177, 36158059, 217166627, 415296747, 1269327263, 8581147923, 85531003291, 307572780863, 417501775143, 594709702027, 1334471501519
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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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, 9, 25 ]
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CROSSREFS
| Cf. A003681, A062094 and A062095.
Sequence in context: A046997 A013488 A186762 * A183939 A145952 A172498
Adjacent sequences: A063420 A063421 A063422 * A063424 A063425 A063426
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KEYWORD
| base,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 09 2001
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