OFFSET
1,1
COMMENTS
Only integers m that satisfy A048138(m) > 1 are considered here.
FORMULA
a(n) = A253302(2*n).
EXAMPLE
The integers whose sum of proper divisors is 16 are 12 and 26, and gcd(12, 26) is 2, so a(1) = 16 (see Example section of A152454).
PROG
(PARI) build(nb) = {vs = vector(nb); nc = nb^2; forcomposite(n=2, nc, val = sigma(n)-n; if (val <= nb, if (vs[val] == 0, vs[val] = -n, vs[val] = gcd(vs[val], n)); ); ); vs[1] = 1; vs; }
lista() = {vd = build(100000); vmax = 80; vr = vector(vmax); forstep (ig=2, vmax, 2, for (i=1, #vd, w = vd[i]; if (w ==ig, vr[ig] = i; break; ); ); ); forstep (i=2, #vr, 2, if (vr[i] == 0, break, print1(vr[i], ", "))); }
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Michel Marcus, Dec 30 2014
STATUS
approved