login
A317045
Numbers k such that A(k+1) = A(k) + 2, where A() = A005100() are the deficient numbers.
3
5, 10, 15, 16, 19, 22, 23, 28, 31, 32, 37, 42, 43, 46, 51, 54, 55, 60, 61, 64, 67, 68, 73, 76, 77, 78, 81, 84, 85, 90, 95, 100, 105, 106, 109, 114, 119, 122, 123, 128, 133, 134, 137, 142, 147, 150, 151, 152, 155, 158, 159, 164, 167, 168, 169, 172, 177, 182
OFFSET
1,1
LINKS
FORMULA
Sequence is { k | A005100(k+1) = A005101(k) + 2 }.
Sequence is { k | A125238(k) = 2 }.
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
A317048 is the main sequence for this entry.
Numbers k such that A(k+1) = A(k) + j, where A() = A005100() are the deficient numbers: A317044 (j=1), this sequence (j=2), A317046 (k=3).
Sequence in context: A313666 A242128 A270926 * A037977 A044845 A313667
KEYWORD
nonn
AUTHOR
Muniru A Asiru, Aug 04 2018
STATUS
approved