A371082 Composite numbers for which A324644(n)/A324198(n) = 2 and sigma(n) == 2 (mod 4).

153, 477, 637, 909, 1017, 1233, 1557, 2097, 3577, 4753, 9457, 10693, 10933, 12393, 13357, 14013, 15337, 17629, 20817, 21097, 21217, 22021, 26353, 29449, 30037, 30717, 31117, 31149, 31797, 32013, 32229, 32337, 32481, 32977, 35557, 35917, 38637, 38725, 41797, 42237, 50029, 53557, 56497, 56677, 56953, 58621, 59437, 60309

Offset

1,1

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[2^16], CompositeQ], GCD[#2, #3]/GCD[#1, #3] == Mod[#2, 4] == 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); };
isA371082(n) = if(isprime(n) || (2!=(sigma(n)%4)), 0, my(u=A276086(n)); (gcd(sigma(n), u)==2*gcd(n, u)));

Crossrefs

Intersection of A191218 and A364286.

Cf. A000203, A276086, A351458.

Sequence in context: A256741 A349696 A246629 * A325376 A256740 A199851

Adjacent sequences: A371079 A371080 A371081 * A371083 A371084 A371085

Keyword

nonn

Author

Antti Karttunen, Mar 10 2024

Status

approved