A291258 - OEIS

A291258

a(n) is the smallest number k such that sigma(k) - phi(k) = n*k, or 0 if no such k exists.

1, 2, 12, 75960, 17156160

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

COMMENTS

a(5) and following terms > 10^13, if they exist. - Giovanni Resta, Aug 21 2017

LINKS

EXAMPLE

a(2) = 12 because sigma(12) = 28, phi(12) = 4; sigma(12) - phi(12) = 2*12 and 12 is the smallest number with this property.

PROG

(PARI) a(n) = {my(k=1); while (sigma(k)-eulerphi(k)!=n*k, k++); k; }

CROSSREFS

KEYWORD

nonn,more

AUTHOR

Altug Alkan, Aug 21 2017

STATUS

approved