A377991 Numbers k such that A351568(k) and A351569(k) are not coprime, where A351568 and A351569 are the sum of divisors of the largest unitary divisor of n that is a square, and of the largest unitary divisor of n that is an exponentially odd number, respectively.

52, 98, 156, 164, 245, 260, 294, 332, 338, 364, 388, 392, 468, 490, 492, 539, 556, 572, 668, 722, 724, 735, 780, 820, 833, 845, 882, 884, 892, 927, 972, 976, 980, 988, 996, 1004, 1014, 1078, 1092, 1125, 1127, 1148, 1164, 1172, 1176, 1196, 1228, 1274, 1300, 1352, 1396, 1404, 1421, 1470, 1476, 1508, 1525, 1568, 1573

Offset

1,1

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for sequences related to sigma(n)

Formula

{k such that gcd(A351568(n),A351569(n)) > 1}.

{k such that A377990(k) > A051027(k)}.

Example

A351568(52) = 7 and A351569(52) = 14, so they share a factor (7), and therefore 52 is included as a term.

Prog

(PARI)
A350388(n) = { my(m=1, f=factor(n)); for(k=1, #f~, if(0==(f[k, 2]%2), m *= (f[k, 1]^f[k, 2]))); (m); };
A351568(n) = sigma(A350388(n));
isA377991(n) = (1<gcd(A351568(n), sigma(n)/A351568(n)));

Crossrefs

Positions k where A377990(k) is larger than A051027(k).

Cf. A350388, A350389, A351568, A351569.

Subsequence of A336548.

Sequence in context: A234099 A026067 A039475 * A274338 A094552 A236461

Adjacent sequences: A377988 A377989 A377990 * A377992 A377993 A377994

Keyword

nonn

Author

Antti Karttunen, Nov 15 2024

Status

approved