OFFSET
1,1
EXAMPLE
550 is in the sequence as it is primitive abundant and it is the smallest primitive abundant number having its prime signature (in this case (1,2,1)). No positive integer < 550 is a primitive abundant and has prime signature (1,2,1).
PROG
(PARI) upto(n) = { m = Map(); res = List(); forfactored(i = 1, n, if(!mapisdefined(m, i[2][, 2]), if(isA071395(i[1]), mapput(m, i[2][, 2], i[1]); listput(res, i[1]) ) ) ); res }
isA071395(v) = {if (sigma(v) <= 2*v, return (0)); fordiv (v, d, if ((d != v) && (sigma(d) >= 2*d), return (0)); ); return (1); } \\ isA071395 from Michel Marcus at A071395
CROSSREFS
KEYWORD
nonn
AUTHOR
David A. Corneth, Oct 20 2022
STATUS
approved