A226944 Numbers k such that 1/k + Sum_{p|k} 1/p > 1.

30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360, 390, 420, 450, 462, 480, 510, 540, 546, 570, 600, 630, 660, 690, 714, 720, 750, 780, 798, 810, 840, 858, 870, 900, 924, 930, 960, 966, 990, 1020, 1050, 1080, 1092, 1110, 1140, 1170, 1200, 1218, 1230

Offset

1,1

Comments

1/k + Sum_{p|k} 1/p = 1 when k is a primary pseudoperfect number (A054377).

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Mathematica

fa=FactorInteger; A[n_] := Sum[1/fa[n][[i, 1]], {i, Length@fa@n}]; Select[1 + Range@1200, A[#] + 1/# > 1 &]

Prog

(PARI) is(n)=my(t=1-1/n); forprime(p=2, 97, if(n%p==0, n/=p^valuation(n, p); t-=1/p; if(t<0, return(1)))); if(n<101^ceil(101*t), return(0)); my(f=factor(n)[, 1]); t<sum(i=1, #f, 1/f[i]) \\ Charles R Greathouse IV, Dec 27 2013

Crossrefs

Cf. A054377.

Sequence in context: A056954 A377952 A246947 * A249674 A050519 A358756

Adjacent sequences: A226941 A226942 A226943 * A226945 A226946 A226947

Keyword

nonn

Author

José María Grau Ribas, Jun 23 2013

Status

approved