A063403 a(1) = 8, 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).

8, 24, 46, 223, 1223, 11223, 87129, 189461, 414621, 2072003, 12072003, 34024001, 163920759, 354640253, 1074732999, 7377145687, 17377145687, 57053304579, 393145173803, 834736688841, 8062231035367, 26899299722333, 27745499695017

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, 8, 25 ]

Crossrefs

Cf. A003681, A062094 and A062095.

Sequence in context: A051062 A152531 A074348 * A355433 A348119 A306415

Adjacent sequences: A063400 A063401 A063402 * A063404 A063405 A063406

Keyword

base,nonn

Author

Robert G. Wilson v, Aug 09 2001

Status

approved