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 1-4 of 4 results.

A075380 Rearrangement of natural numbers so that the sum of two neighboring terms is not squarefree.

Original entry on oeis.org

1, 3, 5, 4, 8, 10, 2, 6, 12, 13, 7, 9, 11, 14, 18, 22, 23, 17, 15, 21, 19, 25, 20, 16, 24, 26, 28, 32, 31, 29, 27, 33, 30, 34, 38, 37, 35, 40, 36, 39, 41, 43, 45, 47, 49, 50, 42, 46, 44, 48, 51, 53, 55, 57, 59, 58, 54, 62, 63, 61, 56, 52, 60, 64, 68, 67, 65, 70, 66, 69, 71, 73
Offset: 1

Views

Author

Amarnath Murthy, Sep 22 2002

Keywords

Comments

Lexicographically earliest permutation of the natural numbers with the defining property; inverse: A167902; A167901(n) = a(a(n)). [Reinhard Zumkeller, Nov 15 2009]

Links

Crossrefs

Cf. A075381.
Cf. A167903, A121878. [Reinhard Zumkeller, Nov 15 2009]

Programs

  • PARI
    v=[1]; n=1; while(n<100, if(!issquarefree(v[#v]+n)&&!vecsearch(vecsort(v), n), v=concat(v, n); n=0); n++); v \\ Derek Orr, Jun 08 2015

Extensions

More terms from David Wasserman, Jan 17 2005

A167901 A075380(A075380(n)).

Original entry on oeis.org

1, 5, 8, 4, 6, 13, 3, 10, 9, 11, 2, 12, 7, 14, 17, 25, 20, 23, 18, 19, 15, 24, 21, 22, 16, 26, 32, 33, 27, 31, 28, 30, 29, 34, 40, 35, 38, 39, 37, 36, 41, 45, 49, 42, 44, 48, 43, 50, 47, 46, 51, 55, 59, 54, 63, 62, 57, 52, 60, 56, 58, 53, 61, 64, 70, 65, 68, 69, 67, 66, 71, 74
Offset: 1

Views

Author

Reinhard Zumkeller, Nov 15 2009

Keywords

Comments

Permutation of positive integers;
a(A075381(n)) = A075381(n);
a(A167902(n)) = A167902(a(n)) = A075380(n).

Links

A167902 Inverse integer permutation to A075380.

Original entry on oeis.org

1, 7, 2, 4, 3, 8, 11, 5, 12, 6, 13, 9, 10, 14, 19, 24, 18, 15, 21, 23, 20, 16, 17, 25, 22, 26, 31, 27, 30, 33, 29, 28, 32, 34, 37, 39, 36, 35, 40, 38, 41, 47, 42, 49, 43, 48, 44, 50, 45, 46, 51, 62, 52, 57, 53, 61, 54, 56, 55, 63, 60, 58, 59, 64, 67, 69, 66, 65, 70, 68, 71, 75
Offset: 1

Views

Author

Reinhard Zumkeller, Nov 15 2009

Keywords

Comments

a(A075381(n)) = A075381(n);
a(A075380(n)) = A075380(a(n)) = n;
a(A167901(n)) = A167901(a(n)) = A121878(n).

Links

A258768 Fixed points in A258767.

Original entry on oeis.org

1, 8, 13, 34, 45, 49, 51, 80, 86, 92, 98, 146, 163, 164, 206, 216, 266, 279, 303, 312, 333, 337, 348, 356, 359, 371, 387, 388, 398, 406, 421, 432, 445, 460, 463, 465, 509, 517, 533, 536, 546, 548, 572, 576, 585, 602, 607, 612, 624, 638, 658, 666, 669, 675, 688, 704, 711, 734, 744, 765, 771, 801, 810, 814
Offset: 1

Views

Author

Derek Orr, Jun 09 2015

Keywords

Comments

Numbers n such that A258767(n) = n.
Also fixed points of A258827. - Reinhard Zumkeller, Jun 11 2015

Links

Crossrefs

Cf. A258767, A075380, A075381, A256271, A258766.
Cf. A258827.

Programs

  • Haskell
    a258768 n = a258768_list !! (n-1)
a258768_list = [x | x <- [1..], a258767 x == x]
-- Reinhard Zumkeller, Jun 11 2015
  • PARI
    print1(1, ", "); v=[1]; n=1; while(#v<10^3, if(!issquarefree(n^2+v[#v]^2)&&!vecsearch(vecsort(v), n), v=concat(v, n); if(n==#v, print1(n, ", ")); n=0); n++)
Showing 1-4 of 4 results.

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

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