cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A333622 Numbers k such that k is divisible by the sum of digits of all the divisors of k in factorial base (A319712).

Original entry on oeis.org

1, 2, 3, 4, 14, 22, 24, 27, 33, 36, 52, 72, 91, 92, 100, 135, 150, 187, 221, 231, 310, 323, 448, 481, 493, 494, 589, 663, 708, 754, 816, 884, 893, 897, 946, 1080, 1155, 1159, 1178, 1200, 1357, 1462, 1475, 1518, 1530, 1536, 1550, 1702, 1710, 1836, 1972, 1978, 2231
Offset: 1

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Author

Amiram Eldar, Mar 29 2020

Keywords

Examples

			14 is a term since its divisors are {1, 2, 7, 14}, their representations in factorial base (A007623) are {1, 10, 101, 210}, and their sum of sums of digits is 1 + (1 + 0) + (1 + 0 + 1) + (2 + 1 + 0) = 7 which is a divisor of 14.
		

Crossrefs

Programs

  • Mathematica
    fctDigSum[n_] := Module[{s=0, i=2, k=n}, While[k > 0, k = Floor[n/i!]; s = s + (i-1)*k; i++]; n-s]; fctDivDigDum[n_] := DivisorSum[n, fctDigSum[#] &]; Select[Range[10^3], Divisible[#, fctDivDigDum[#]] &] (* after Jean-François Alcover at A034968 *)

A319715 Sum of A276150(d) over divisors d of n, where A276150 gives the sum of digits in primorial base.

Original entry on oeis.org

1, 2, 3, 4, 4, 5, 3, 6, 6, 8, 5, 9, 4, 7, 10, 10, 6, 11, 5, 14, 10, 11, 7, 15, 9, 10, 12, 15, 8, 16, 3, 12, 10, 10, 10, 17, 4, 9, 10, 20, 6, 18, 5, 17, 18, 13, 7, 23, 8, 18, 14, 18, 8, 22, 14, 23, 14, 16, 9, 26, 4, 7, 17, 16, 12, 20, 5, 16, 14, 22, 7, 27, 6, 10, 21, 17, 14, 22, 7, 30, 19, 14, 9, 34, 16, 13, 18, 27, 10, 30, 10, 19, 10
Offset: 1

Views

Author

Antti Karttunen, Oct 02 2018

Keywords

Comments

Inverse Möbius transform of A276150.

Crossrefs

Programs

  • Mathematica
    d[n_] := Module[{k = n, p = 2, s = 0, r}, While[{k, r} = QuotientRemainder[k, p]; k != 0 || r != 0, s += r; p = NextPrime[p]]; s]; a[n_] := DivisorSum[n, d[#] &]; Array[a, 100] (* Amiram Eldar, Mar 05 2024 *)
  • PARI
    A276150(n) = { my(s=0, p=2, d); while(n, d = (n%p); s += d; n = (n-d)/p; p = nextprime(1+p)); (s); };
    A319715(n) = sumdiv(n,d,A276150(d));

Formula

a(n) = Sum_{d|n} A276150(d).
a(n) = A319713(n) + A276150(n).

A319711 Sum of A034968(d) over proper divisors d of n, where A034968 gives the sum of digits in factorial base.

Original entry on oeis.org

0, 1, 1, 2, 1, 4, 1, 4, 3, 5, 1, 7, 1, 4, 6, 6, 1, 8, 1, 10, 5, 6, 1, 11, 4, 5, 6, 9, 1, 15, 1, 10, 7, 7, 6, 15, 1, 6, 6, 16, 1, 15, 1, 13, 13, 8, 1, 16, 3, 10, 8, 9, 1, 14, 8, 14, 7, 6, 1, 25, 1, 5, 13, 13, 7, 18, 1, 13, 9, 18, 1, 21, 1, 6, 12, 12, 7, 15, 1, 25, 9, 8, 1, 26, 9, 7, 7, 20, 1, 29, 6, 16, 6, 9, 8, 21, 1, 10, 14, 19, 1, 18, 1, 15, 22
Offset: 1

Views

Author

Antti Karttunen, Oct 02 2018

Keywords

Crossrefs

Programs

  • Mathematica
    d[n_] := Module[{k = n, m = 2, s = 0, r}, While[{k, r} = QuotientRemainder[k, m]; k != 0 || r != 0, s += r; m++]; s]; a[n_] := DivisorSum[n, d[#] &, # < n &]; Array[a, 100] (* Amiram Eldar, Mar 05 2024 *)
  • PARI
    A034968(n) = { my(s=0, b=2, d); while(n, d = (n%b); s += d; n = (n-d)/b; b++); (s); };
    A319711(n) = sumdiv(n,d,(dA034968(d));

Formula

a(n) = Sum_{d|n, dA034968(d).
a(n) = A319712(n) - A034968(n).
Showing 1-3 of 3 results.