A086360 Fixed point if (decimal-digit-sum)-function at initial value = n-th primorial = A002110(n) is iterated.

2, 6, 3, 3, 6, 6, 3, 3, 6, 3, 3, 3, 6, 6, 3, 6, 3, 3, 3, 6, 6, 6, 3, 6, 6, 3, 3, 6, 6, 3, 3, 6, 3, 3, 6, 6, 6, 6, 3, 6, 3, 3, 6, 6, 3, 3, 3, 3, 6, 6, 3, 6, 6, 3, 6, 3, 6, 6, 6, 3, 3, 6, 6, 3, 3, 6, 6, 6, 3, 3, 6, 3, 3, 3, 3, 6, 3, 3, 6, 6, 3, 3, 6, 6, 6, 3, 6

Offset

1,1

Links

Nathaniel Johnston, Table of n, a(n) for n = 1..10000

Formula

a(n) = A010888(A002110(n)) = fixed-point of A007953(A002110(n));

a(n) = n-th primorial modulo(9).

Only a(1)=2; each subsequent term is a 3 or a 6.

Example

For n=7, 7th primorial = 510510, iteration list = {510510,12,3}, so a(7)=3.

Maple

A086360 := proc(n) option remember: if(n=1)then return 2:fi: return ithprime(n)*procname(n-1) mod 9: end: seq(A086360(n), n=1..100); # Nathaniel Johnston, May 04 2011

Mathematica

sud[x_] := Apply[Plus, DeleteCases[IntegerDigits[x], 0]] q[x_] := Apply[Times, Table[Prime[w], {w, 1, x}]] Table[FixedPoint[sud, q[w]], {w, 1, 128}]

Crossrefs

Cf. A086353-A086361, A007953, A002110, A010888, A038194, A029898.

Sequence in context: A321873 A218256 A198418 * A066098 A299160 A123733

Adjacent sequences: A086357 A086358 A086359 * A086361 A086362 A086363

Keyword

base,easy,nonn

Author

Labos Elemer, Jul 21 2003

Status

approved