OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
MAPLE
with(numtheory): A:=select(n->sigma(n)>2*n, [$1..1000]): a:=select(j->A[j+1]=A[j]+4, [$1..nops(A)-1]);
MATHEMATICA
Position[Map[{#1, #2 - 4} & @@ # &, Partition[Select[Range[10^3], DivisorSigma[1, #] > 2 # &], 2, 1]], _?(SameQ @@ # &)][[All, 1]] (* Michael De Vlieger, Jun 29 2018 *)
PROG
(GAP) A:=Filtered([1..1000], n->Sigma(n)>2*n);; a:=Filtered([1..Length(A)-1], i->A[i+1]=A[i]+4);
(PARI) list(lim) = {my(k = 1, k2, m = 0); for(k2 = 2, lim, if(sigma(k2, -1) > 2, if(k2 == k1 + 4, print1(m, ", ")); m++; k1 = k2)); } \\ Amiram Eldar, Mar 01 2025
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Muniru A Asiru, Jun 25 2018
STATUS
approved