login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A342672
a(n) = lcm(sigma(n), A003961(n)), where A003961 is fully multiplicative with a(prime(k)) = prime(k+1), and sigma is the sum of divisors of n.
3
1, 3, 20, 63, 42, 60, 88, 135, 325, 126, 156, 1260, 238, 264, 840, 2511, 342, 975, 460, 126, 1760, 468, 696, 540, 1519, 714, 1000, 5544, 930, 2520, 1184, 1701, 3120, 1026, 3696, 20475, 1558, 1380, 4760, 1890, 1806, 5280, 2068, 3276, 13650, 2088, 2544, 50220, 6897, 4557, 6840, 14994, 3186, 3000, 6552, 11880, 1840, 2790
OFFSET
1,2
FORMULA
a(n) = lcm(A000203(n), A003961(n)).
a(n) = A341529(n) / A342671(n).
PROG
(PARI)
A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A342672(n) = lcm(sigma(n), A003961(n));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Mar 20 2021
STATUS
approved