A105365 Rearrangement of positive integers according to parity of (prime(n)-1)/2 (see comments).

1, 4, 2, 6, 8, 3, 5, 9, 10, 7, 12, 11, 13, 14, 15, 17, 16, 19, 18, 20, 23, 21, 22, 29, 31, 37, 24, 25, 41, 43, 26, 27, 47, 28, 53, 30, 59, 32, 33, 61, 34, 67, 35, 71, 73, 36, 38, 39, 40, 79, 83, 42, 89, 44, 97, 45, 101, 46, 103, 107

Offset

1,2

Comments

a(1)=1, for n>1: if (prime(n)-1)/2 is even/odd then a(n) is the next prime/composite number.

Links

Table of n, a(n) for n=1..60.

Mathematica

p=Prime[Range[100]]; s=Complement[Range[100], p]; bb={1}; is=1; ip=0; Do[If[OddQ[(Prime[i]-1)/2], is=is+1; bb=Append[bb, s[[is]]], ip=ip+1; bb=Append[bb, p[[ip]]]], {i, 2, 60}]; bb

Crossrefs

Cf. A105366.

Sequence in context: A138947 A083412 A086399 * A077157 A268718 A306874

Adjacent sequences: A105362 A105363 A105364 * A105366 A105367 A105368

Keyword

nonn

Author

Zak Seidov, Apr 01 2005

Status

approved