A037280 If n is composite replace n with the concatenation of its nontrivial divisors [ A037279 ] then divide out any factors of 2.

1, 1, 3, 1, 5, 23, 7, 3, 3, 25, 11, 1173, 13, 27, 35, 31, 17, 2369, 19, 12255, 37, 211, 23, 586703, 5, 213, 39, 12357, 29, 23561015, 31, 1551, 311, 217, 57, 117345609, 37, 219, 313, 6145255, 41, 23671421, 43, 120561, 35915, 223, 47, 2933515203, 7, 251025, 317

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy
• base

Examples

			Divisors of 12 are 1,2,3,4,6,12, so 12 -> 2346 = 2*1173 -> 1173 = a(12).
		

Crossrefs

Cf. A037279.

Programs

Maple

with(numtheory):ds:=proc(s) local j: RETURN(add(s[j]*10^(j-1),j=1..nops(s))):end: a:=proc(n) options remember: local d,i,l,m: if n<3 then RETURN(1) else if not isprime(n) then d:=divisors(n): l:=nops(d): m:=ds([seq(op(convert(d[l-i+1],base,10)),i=2..l-1)]): RETURN(m/piecewise(m mod 2=1,1,2^(ifactors(m)[2][1][2]))) else RETURN(n) fi fi: end; seq(a(n),n=1..70); # C. Ronaldo

Extensions

More terms from Erich Friedman