A322582 -id:A322582 - cp's OEIS frontend

A351443 Odd numbers k for which A003958(sigma(k)) = A003958(k), where A003958 is multiplicative with a(p^e) = (p-1)^e and sigma is the sum of divisors function.

1, 49, 40905, 106353, 140211, 275301, 302697, 499041, 597213, 1094913, 1284417, 1578933, 2004345, 2266137, 2560653, 3247857, 3444201, 3738717, 4425921, 5014953, 5123817, 5211297, 5407641, 5505813, 5996673, 6193017, 6870339, 7174737, 8156457, 8941833, 9432693, 9825381, 9923553

Offset: 1

Antti Karttunen, Feb 12 2022

nonn

Odd numbers k for which A351442(k) = A003958(k), or equally, for which k = A351444(k) = A322582(k) + A351442(k).

The 13th term, 2004345, is one of the rare abundant numbers (A005101, A005231) in this sequence.

Odd terms in A351446.
Cf. A000203, A003958, A005101, A005231, A322582, A351442, A351444, A351445.
These terms doubled form a subsequence of A351447.

A003958(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1]--); factorback(f); };
A351442(n) = A003958(sigma(n));
isA351443(n) = ((n%2) && (A351442(n)==A003958(n)));

A351444 a(n) = n - A003958(n) + A003958(sigma(n)), where A003958 is multiplicative with a(p^e) = (p-1)^e and sigma is the sum of divisors function.

Original entry on oeis.org

1, 3, 2, 9, 3, 6, 2, 15, 17, 10, 3, 16, 7, 10, 9, 45, 5, 38, 5, 28, 10, 16, 3, 30, 39, 26, 23, 28, 9, 26, 2, 55, 15, 26, 13, 104, 19, 28, 21, 52, 13, 32, 11, 46, 53, 28, 3, 76, 49, 94, 23, 76, 9, 54, 19, 58, 25, 46, 9, 64, 31, 34, 51, 189, 29, 50, 17, 76, 27, 50, 5, 164, 37, 74, 73, 82, 19, 66, 5, 136

Offset: 1

Antti Karttunen, Feb 12 2022

nonn

Antti Karttunen, Table of n, a(n) for n = 1..20000
Index entries for sequences related to sigma(n)

Cf. A000203, A003958, A322582, A351442, A351445.

Cf. A351446 (fixed points), A351443 (odd terms there).

A003958(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1]--); factorback(f); };
A351444(n) = (n - A003958(n) + A003958(sigma(n)));

a(n) = A322582(n) + A351442(n) = n - A003958(n) + A003958(sigma(n)).

a(n) = n + A351445(n).

A348928 a(n) = gcd(n, A003958(n)), where A003958 is multiplicative with a(p^e) = (p-1)^e.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 4, 3, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 4, 1, 2, 3, 4, 1, 6, 1, 2, 1, 2, 1, 2, 1, 2, 1, 4, 1, 2, 5, 2, 3, 2, 1, 4, 1, 2, 3, 1, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 2, 1, 6, 1, 4, 1, 2, 1, 12, 1, 2, 1, 2, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 1, 4, 1, 2, 1, 4, 3

Offset: 1

Antti Karttunen, Nov 07 2021

Antti Karttunen, Table of n, a(n) for n = 1..65537

Cf. A003958, A085731, A126865, A322582, A348929, A348998 [= a(A276086(n))].

Differs from similar A126864 for the first time at n=36, where a(36) = 4, while A126864(36) = 2.

f[p_, e_] := (p - 1)^e; a[n_] := GCD[n, Times @@ f @@@ FactorInteger[n]]; Array[a, 100] (* Amiram Eldar, Nov 07 2021 *)

A003958(n) = if(1==n,n,my(f=factor(n)); for(i=1,#f~,f[i,1]--); factorback(f));
A348928(n) = gcd(n, A003958(n));

a(n) = gcd(n, A003958(n)) = gcd(n, A322582(n)) = gcd(A003958(n), A322582(n)).

A348975 a(n) = A003415(n) + A003958(n) - n, where A003415 is the arithmetic derivative and A003958 is fully multiplicative with a(p) = (p-1).

Original entry on oeis.org

0, 0, 0, 1, 0, 1, 0, 5, 1, 1, 0, 6, 0, 1, 1, 17, 0, 7, 0, 8, 1, 1, 0, 22, 1, 1, 8, 10, 0, 9, 0, 49, 1, 1, 1, 28, 0, 1, 1, 32, 0, 11, 0, 14, 10, 1, 0, 66, 1, 11, 1, 16, 0, 35, 1, 42, 1, 1, 0, 40, 0, 1, 12, 129, 1, 15, 0, 20, 1, 13, 0, 88, 0, 1, 12, 22, 1, 17, 0, 100, 43, 1, 0, 52, 1, 1, 1, 62, 0, 49, 1, 26, 1, 1, 1

Offset: 1

Antti Karttunen, Nov 09 2021

No negative terms. See comments in A322582.

This is the difference between the arithmetic derivative of n [= A003415(n)] and its guaranteed lower bound A322582(n) [= n - A003958(n)].

Antti Karttunen, Table of n, a(n) for n = 1..16384

Cf. A003415, A003958, A168036, A322582.

Cf. also A348970 for the corresponding difference from a guaranteed upper bound.

MapAt[# + 1 &, Array[If[# < 2, 0, # Total[#2/#1 & @@@ #2]] + Times @@ Map[(#1 - 1)^#2 & @@ # &, #2] - #1 & @@ {#, FactorInteger[#]} &, 95], 1] (* Michael De Vlieger, Mar 15 2022 *)

A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
A003958(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1]--); factorback(f); };
A322582(n) = (n-A003958(n));
A348975(n) = (A003415(n) - A322582(n));

a(n) = A003415(n) - A322582(n).

a(n) = A003958(n) + A168036(n).

cp's OEIS Frontend

A351443 Odd numbers k for which A003958(sigma(k)) = A003958(k), where A003958 is multiplicative with a(p^e) = (p-1)^e and sigma is the sum of divisors function.

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A351444 a(n) = n - A003958(n) + A003958(sigma(n)), where A003958 is multiplicative with a(p^e) = (p-1)^e and sigma is the sum of divisors function.

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A348928 a(n) = gcd(n, A003958(n)), where A003958 is multiplicative with a(p^e) = (p-1)^e.

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A348975 a(n) = A003415(n) + A003958(n) - n, where A003415 is the arithmetic derivative and A003958 is fully multiplicative with a(p) = (p-1).

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