A070287 Numbers k such that the equation lcm(sigma(x),phi(x))=k has solutions.

1, 3, 4, 12, 14, 24, 28, 36, 48, 60, 72, 78, 84, 96, 120, 144, 168, 180, 192, 240, 248, 264, 288, 312, 336, 360, 420, 432, 480, 496, 576, 620, 672, 684, 720, 780, 792, 798, 840, 864, 924, 936, 960, 1008, 1056, 1080, 1092, 1104, 1176, 1240, 1260, 1344, 1368

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..5000

Maple

N:= 2000: # for terms <= N
S:= select(`<=`, {seq(ilcm(NumberTheory:-sigma(x), NumberTheory:-phi(x)), x=1..N)}, N):
sort(convert(S, list)); # Robert Israel, Jun 08 2026

Prog

(PARI) for(n=1, 2000, if(0<sum(i=1, n, if(lcm(sigma(i), eulerphi(i))-n, 0, 1)), print1(n, ", ")))

Crossrefs

Includes A084921. Cf. A009286.

Sequence in context: A094025 A376979 A336612 * A124637 A352907 A047173

Adjacent sequences: A070284 A070285 A070286 * A070288 A070289 A070290

Keyword

easy,nonn

Author

Benoit Cloitre, May 10 2002

Status

approved