A075695 a(1)=1, then "jump over two primes": a(n) = 2*nextprime(nextprime(a(n-1))) - a(n-1).

1, 5, 17, 29, 45, 61, 81, 97, 109, 145, 157, 177, 185, 201, 245, 269, 285, 329, 345, 353, 381, 397, 421, 445, 469, 505, 537, 557, 581, 605, 621, 661, 693, 725, 741, 761, 785, 809, 833, 873, 889, 933, 949, 985, 1009, 1029, 1037, 1061, 1077, 1105, 1129, 1177

Offset

1,2

Comments

The rule "jump over next something" can be changed. A075694 gives the simplest example: "jump over next prime".

Links

Matthew House, Table of n, a(n) for n = 1..10000

Formula

a(1)=1, a(n) = 2*nextprime(nextprime(a(n-1)))-a(n-1).

Example

a(1)=1; next second prime (second smallest larger than a(1))=3; "jump over" it: 3+(3-1)=5; a(2)=5; next second prime (second smallest larger than a(2))=11; "jump over" it: 11+(11-5)=17.

Maple

a(1) := 1; a(n)=2*nextprime(nextprime(a(n-1)))-a(n-1);

Prog

(PARI) np(k)=my(m=k+1); while(!isprime(m), m++); m;
first(m)=my(v=vector(m)); v[1]=1; for(i=2, m, v[i]=2*np(np(v[i-1]))-v[i-1]; ); v; /* Anders Hellström, Aug 08 2015 */
(Magma) [n le 1 select 1 else 2*NextPrime(NextPrime(Self(n-1)))-Self(n-1): n in [1..55]]; // Vincenzo Librandi, Aug 09 2015

Crossrefs

Cf. A075694.

Sequence in context: A071695 A242025 A027703 * A146278 A034937 A024351

Adjacent sequences: A075692 A075693 A075694 * A075696 A075697 A075698

Keyword

easy,nonn

Author

Zak Seidov, Sep 26 2002

Status

approved