OFFSET
1,1
COMMENTS
An integer n is included if, for some value y >= 0: n = A007918(A000196(n) + y) * A007918(A000196(n) - y) Or: n = nextprime(sqrtint(n) + y) * nextprime(sqrtint(n) - y) Where "nextprime(x)" is the smallest prime number >= to x and "sqrtint(z)" is the integer part of the square root of z.
Has many terms in common with A078972. - Bill McEachen, Dec 24 2020
LINKS
Michel Marcus, Table of n, a(n) for n = 1..3406
EXAMPLE
25 = nextprime(5 + 0) * nextprime(5 - 0) = 5 * 5 = 25
35 = nextprime(5 + 1) * nextprime(5 - 1) = 7 * 5 = 35
119 = nextprime(10 + 4) * nextprime(10 - 4) = 17 * 7 = 119
PROG
(PARI) bal(x, y) = nextprime(sqrtint(x)+y) * nextprime(sqrtint(x)-y);
findbal(x) = local(z, y); z=sqrtint(x); while( 0<=z, y=bal(x, z); if(y==x, print1(x", "); break; ); z--; );
for (n=1, 1200, findbal(n));
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew S. Plewe, Nov 13 2007
STATUS
approved