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

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

Author

Amarnath Murthy, Sep 22 2002

Keywords

• nonn

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

• Scott R. Shannon, Table of n, a(n) for n = 1..10000
• Index entries for sequences that are permutations of the natural numbers [_Reinhard Zumkeller_, Nov 15 2009]

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