A063382 a(1) = 5, 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).

5, 15, 35, 57, 319, 1129, 11129, 31359, 310453, 1691837, 7241691, 15094799, 31486929, 159198031, 1159198031, 6203186877, 11721529237, 88429132553, 129487682919, 1228291054211, 1394483927247, 8800411584567, 34329256355023

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, 5, 24 ]

Crossrefs

Cf. A003681, A062094 and A062095.

Sequence in context: A034052 A233348 A061829 * A069983 A005894 A015622

Adjacent sequences: A063379 A063380 A063381 * A063383 A063384 A063385

Keyword

base,nonn

Author

Robert G. Wilson v, Aug 08 2001

Status

approved