OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MAPLE
with(numtheory): A:=select(k->sigma(k)<2*k, [$1..300]):
a:=select(j->A[j+1]=A[j]+2, [$1..nops(A)-1]);
MATHEMATICA
Position[Differences[Select[Range[250], DivisorSigma[1, #] < 2*# &]], 2] // Flatten (* Amiram Eldar, Mar 15 2024 *)
PROG
(GAP) A:=Filtered([1..300], k->Sigma(k)<2*k);; a:=Filtered([1..Length(A)-1], i->A[i+1]=A[i]+2);
CROSSREFS
KEYWORD
nonn
AUTHOR
Muniru A Asiru, Aug 04 2018
STATUS
approved