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URL: https://oeis.org/A303741

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A303741
Numbers k such that A(k+1) = A(k) + 2, where A() = A005101() are the abundant numbers.
5
2, 7, 10, 14, 16, 19, 22, 23, 26, 31, 36, 39, 44, 45, 48, 51, 52, 59, 62, 65, 70, 71, 74, 79, 81, 82, 83, 86, 87, 90, 93, 96, 99, 104, 107, 110, 111, 114, 118, 120, 125, 128, 131, 133, 135, 138, 141, 146, 149, 150, 155, 156, 158, 164, 169, 170, 175, 178, 179
OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..5000 from Muniru A Asiru)
FORMULA
Sequence is { k | A005101(k+1) = A005101(k) + 2 }.
a(n) = A091194(A231086(n)). - Amiram Eldar, Mar 01 2025
MAPLE
with(numtheory): A:=select(n->sigma(n)>2*n, [$1..1000]): a:=select(j->A[j+1]=A[j]+2, [$1..nops(A)-1]);
MATHEMATICA
Position[Differences[Select[Range[750], DivisorSigma[1, #] > 2*# &]], 2] // Flatten (* Amiram Eldar, Mar 15 2024 *)
PROG
(GAP) A:=Filtered([1..1000], n->Sigma(n)>2*n);; a:=Filtered([1..Length(A)-1], i->A[i+1]=A[i]+2);
(PARI) list(lim) = {my(k = 1, k2, m = 0); for(k2 = 2, lim, if(sigma(k2, -1) > 2, if(k2 == k1 + 2, print1(m, ", ")); m++; k1 = k2)); } \\ Amiram Eldar, Mar 01 2025
CROSSREFS
A231086 is the main entry for this sequence.
Sequence in context: A297832 A003158 A130336 * A085303 A304799 A349499
KEYWORD
nonn
AUTHOR
Muniru A Asiru, Jun 22 2018
STATUS
approved