A065002 Integers m such that A064992(m) = A064992(m+1).

2, 3, 7, 75, 86, 91, 1863, 2763, 3595, 5451, 6031, 7734, 8023, 9631, 35403, 41391, 53431, 63847, 64294, 148391, 205556, 237992, 374715, 381440, 404775, 442755, 510283, 546422, 917035, 1149111, 1291895, 1563158, 2197526, 2610182, 2693035, 2730524, 2804331, 3020715, 3547982, 4365950

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..138 (terms below 10^10)

Mathematica

usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); seq = {}; u1 = usigma[1]; u2 = usigma[2]; Do[u3 = usigma[n]; If[u3 == 2*u2 - u1, AppendTo[seq, n - 2]]; u1 = u2; u2 = u3, {n, 3, 10^4}]; seq (* Amiram Eldar, Jan 04 2020 *)

Prog

(PARI) usigma(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d));
lista(nn) = {u = vector(nn, n, usigma(n)); v = vector(#u-1, n, u[n+1] - u[n]); w = vector(#v-1, n, v[n+1] - v[n]); x = select(y->y==0, w, 1); } \\ Michel Marcus, Aug 12 2018

Crossrefs

Cf. A064992.

Sequence in context: A035094 A084729 A101117 * A288800 A247025 A053964

Adjacent sequences: A064999 A065000 A065001 * A065003 A065004 A065005

Keyword

nonn

Author

Jason Earls, Nov 01 2001

Extensions

More terms from Michel Marcus, Aug 12 2018

Status

approved