A014686 In sequence of prime numbers add 1 to first prime, 3rd prime, fifth prime, ... then subtract 1 from 2nd prime, fourth prime, sixth prime and so on.

3, 2, 6, 6, 12, 12, 18, 18, 24, 28, 32, 36, 42, 42, 48, 52, 60, 60, 68, 70, 74, 78, 84, 88, 98, 100, 104, 106, 110, 112, 128, 130, 138, 138, 150, 150, 158, 162, 168, 172, 180, 180, 192, 192, 198, 198, 212, 222, 228, 228, 234, 238, 242, 250, 258, 262, 270, 270

Offset: 1

Author

Mohammad K. Azarian

Keywords

• nonn
• easy

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Programs

Mathematica

Module[{nn=60},Total/@Partition[Riffle[Prime[Range[nn]],{1,-1},{2,-1,2}],2]] (* Harvey P. Dale, Oct 04 2019 *)

Formula

a(n)=prime(n)-(-1)^n=A000040(n)-A033999(n+1). [From Juri-Stepan Gerasimov, Sep 11 2009]

Extensions

More terms from Andrew J. Gacek (andrew(AT)dgi.net)