OFFSET
1,2
PROG
(PARI) isok(n) = (sigma(n)-n == primepi(n)) \\ Michel Marcus, Jul 14 2013
CROSSREFS
KEYWORD
nonn,more
AUTHOR
EXTENSIONS
More terms from Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Apr 09 2002
a(16)-a(17) from Donovan Johnson, Sep 03 2008
a(18) from Giovanni Resta, Jul 05 2016
STATUS
approved