A120318 Consecutive refactorable numbers a(n)-1, a(n) in which 11 is the smallest prime divisor of a(n).

38604666779024731098340977806401, 7208577773559712596404976530284801, 695314235787112476661749457231833601, 313468146036745542621075945985861000534849

Offset

1,1

Links

Table of n, a(n) for n=1..4.

Formula

a(n) is the first integer of the form (11*k)^(11-1) such that both a(n) and a(n)-1 is refactorable and 11 is the smallest prime divisor of a(n).

Maple

with(numtheory); RFC11:=[]: p:=ithprime(5): P:=[seq(ithprime(i), i=1..4)]; for w to 1 do for k from 3 to 12^4 by 2 do if andmap(z -> k mod z <> 0, P) then m:=p*k; n:=m^(p-1); t:=tau(n); n1:=n-1; t1:=tau(n1); if (n mod t = 0) and (n1 mod t1 = 0) then RFC11:=[op(RFC11), n]; print(ifactor(n)); fi fi; od od;

Crossrefs

Cf. A033950, A036898, A114617.

Sequence in context: A104319 A003943 A003936 * A356072 A338982 A338966

Adjacent sequences: A120315 A120316 A120317 * A120319 A120320 A120321

Keyword

nonn

Author

Walter Kehowski, Jun 20 2006

Status

approved