A171669 Pell numbers sandwiched between two numbers having same number of divisors.

12, 5741, 2744210, 15994428, 21300003689580, 723573111879672, 1111984844349868137938112

Offset

1,1

Links

Table of n, a(n) for n=1..7.

Mathematica

f[n_]:=Length[Divisors[n]]; a=1; b=0; c=0; lst={}; Do[c=a+b+c; If[f[c-1]==f[c+1], AppendTo[lst, c]]; a=b; b=c, {n, 80}]; lst

Crossrefs

Cf. A000129, A005237, A005238, A067889, A171666, A171667, A171668

Sequence in context: A013508 A230749 A003793 * A094268 A208865 A012607

Adjacent sequences: A171666 A171667 A171668 * A171670 A171671 A171672

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Dec 14 2009

Status

approved