OFFSET
0,3
COMMENTS
In the classification every class contains no more than a finite number of numbers with a given least prime divisor.
LINKS
Indranil Ghosh, Table of n, a(n) for n = 0..1000
Vladimir Shevelev, A classification of the positive integers over primes
FORMULA
For n>=3, a(n) = (prime(n)^2 - prime(n-1)^2)/2.
EXAMPLE
a(6) = (prime(6)^2 - prime(5)^2)/2 = (13^2 - 11^2)/2 = 24. - Indranil Ghosh, Mar 08 2017
MAPLE
A247396:=n->(ithprime(n)^2 - ithprime(n-1)^2)/2: 0, 1, 3, seq(A247396(n), n=3..100); # Wesley Ivan Hurt, Apr 18 2017
MATHEMATICA
a[0] = 0; a[1] = 1; a[2] = 3; a[n_] := (Prime[n]^2 - Prime[n - 1]^2) / 2; Table[a[n], {n, 0, 53}] (* Indranil Ghosh, Mar 08 2017 *)
PROG
(PARI) for(n=0, 53, print1(if(n>2, (prime(n)^2 - prime(n - 1)^2)/2, if(n<2, n, 3)), ", ")) \\ Indranil Ghosh, Mar 08 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Sep 16 2014
EXTENSIONS
More terms from Peter J. C. Moses, Sep 17 2014
STATUS
approved