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.

A077663 Sum of terms of n-th row of A077661.

Original entry on oeis.org

1, 6, 18, 20, 75, 32, 196, 72, 135, 92, 726, 117, 1183, 184, 258, 272, 2601, 257, 3610, 351, 541, 464, 6348, 450, 1625, 652, 1134, 712, 12615, 632, 15376, 1056, 1427, 1124, 2007, 999, 26011, 1408, 2032, 1367, 35301, 1261, 40678, 1816, 2219, 2072, 53016, 1764
Offset: 1

Views

Author

Amarnath Murthy, Nov 14 2002

Keywords

Comments

a(p) = p^2*(p+1)/2.
a(2^n) = n*(n+1).

Crossrefs

Cf. A077661, A077662.

Extensions

More terms from Sascha Kurz, Jan 27 2003

A081520 Triangle read by rows in which row n consists of 1 and the n-1 smallest positive numbers having common factors with n.

Original entry on oeis.org

1, 1, 2, 1, 3, 6, 1, 2, 4, 6, 1, 5, 10, 15, 20, 1, 2, 3, 4, 6, 8, 1, 7, 14, 21, 28, 35, 42, 1, 2, 4, 6, 8, 10, 12, 14, 1, 3, 6, 9, 12, 15, 18, 21, 24, 1, 2, 4, 5, 6, 8, 10, 12, 14, 15, 1, 11, 22, 33, 44, 55, 66, 77, 88, 99, 110, 1, 2, 3, 4, 6, 8, 9, 10, 12, 14, 15, 16, 1, 13, 26, 39, 52, 65, 78
Offset: 1

Views

Author

Amarnath Murthy, Mar 27 2003

Keywords

Examples

			1;
1, 2;
1, 3, 6;
1, 2, 4, 6;
1, 5,10,15,20;
1, 2, 3, 4, 6, 8;
1, 7,14,21,28,35,42;
...

Links

Crossrefs

Cf. A081518, A081519, A077661.

Programs

  • Maple
    arow:= proc(n) local L;
  L:= select(t -> igcd(t,n) > 1, [$1..n^2]);
  1,op(L[1..n-1]);
end proc:
seq(arow(n),n=1..20); # Robert Israel, May 21 2015
  • Mathematica
    Table[Join[{1}, Select[Range[n^2], GCD[n, #] > 1 &, n - 1]], {n, 1, 13}] // Flatten (* Ivan Neretin, May 21 2015 *)
  • PARI
    for(n=1,5,print1("\n1"); for(i=1,n-1,print1(", "i*n))) \\ Charles R Greathouse IV, May 21 2015

Extensions

More terms from Ryan Propper, Nov 05 2005
Name edited by Robert Israel, May 21 2015

A077662 a(n) = n-th positive integer not relatively prime to n, with a(1)=1.

Original entry on oeis.org

1, 4, 9, 8, 25, 9, 49, 16, 27, 16, 121, 18, 169, 24, 33, 32, 289, 27, 361, 34, 49, 40, 529, 36, 125, 48, 81, 49, 841, 40, 961, 64, 84, 64, 112, 54, 1369, 72, 102, 66, 1681, 58, 1849, 80, 96, 88, 2209, 72, 343, 84, 136, 96, 2809, 81, 200, 98, 153, 112, 3481, 82
Offset: 1

Views

Author

Amarnath Murthy, Nov 14 2002

Keywords

Comments

Final term of n-th row of A077661.

Links

Crossrefs

Cf. A077661, A077663, A069213.
A077149(n) - n - 1.

Programs

  • Mathematica
    Join[{1},Table[Select[Range[5000],!CoprimeQ[#,n]&][[n]],{n,2,60}]] (* Harvey P. Dale, May 26 2023 *)
  • PARI
    a(n) = local(i, k); if(n<=1,n,k=n-eulerphi(n);i=n\k;k*=i;i*=n; while(k

Extensions

More terms from Sascha Kurz, Jan 27 2003
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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