A364286 Composite numbers k for which A324644(k)/A324198(k) = 2.

33, 51, 69, 91, 99, 135, 141, 145, 153, 159, 187, 207, 213, 217, 285, 295, 303, 321, 339, 391, 411, 423, 427, 435, 445, 477, 507, 519, 573, 637, 639, 679, 681, 699, 771, 783, 799, 843, 855, 861, 885, 895, 901, 909, 933, 951, 963, 1017, 1041, 1057, 1059, 1071, 1081, 1083, 1147, 1149, 1173, 1185, 1195, 1203, 1207

Offset

1,1

Comments

See comments in A351458.

All terms are odd. Of the 63 initial terms of A349169, only term 13923 occurs also in this sequence. The first common term with A332458 is 161257. - Antti Karttunen, Mar 10 2024

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Index entries for sequences where odd perfect numbers must occur, if they exist at all

Index entries for sequences related to primorial base

Index entries for sequences related to sigma(n)

Mathematica

f[x_] := Block[{m, i, n = x, p}, m = i = 1; While[n > 0, p = Prime[i]; m *= p^Mod[n, p]; n = Quotient[n, p]; i++]; m]; Select[Select[Range[1350], CompositeQ], GCD[#2, #3]/GCD[#1, #3] == 2 & @@ {#, DivisorSigma[1, #], f[#]} &] (* Michael De Vlieger, Mar 10 2024 *)

Prog

(PARI)
A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
isA364286(n) = if(isprime(n), 0, my(u=A276086(n)); (gcd(sigma(n), u)==2*gcd(n, u))); \\ Antti Karttunen, Mar 10 2024

Crossrefs

Cf. A000203, A276086, A324198, A324644, A332458, A349169, A351458, A371082 (subsequence).

Subsequence of A082686.

Sequence in context: A204381 A034815 A014976 * A109407 A204374 A261107

Adjacent sequences: A364283 A364284 A364285 * A364287 A364288 A364289

Keyword

nonn

Author

Antti Karttunen, Jul 17 2023

Status

approved