A349809 a(n) = n^2 - A099611(n).

1, 4, 1, 10, 7, 4, 5, 2, 1, 8, 9, 4, 3, 2, 1, 6, 5, 4, 3, 2, 3, 2, 5, 6, 3, 6, 1, 2, 13, 8, 7, 6, 3, 6, 3, 4, 9, 2, 1, 6, 7, 4, 11, 8, 13, 6, 3, 2, 3, 2, 3, 8, 3, 2, 11, 8, 1, 6, 3, 6, 9, 2, 3, 2, 5, 4, 3, 8, 1, 2, 3, 6, 3, 8, 3, 2, 5, 2, 7, 2, 3, 2, 5, 6, 5, 6

Offset

4,2

Links

Hugo Pfoertner, Table of n, a(n) for n = 4..10000

Prog

(PARI) for(n=4, 89, my(n2=n*n); forstep(k=n2, 1, -1, if(k%2==1&&omega(k)==2&&bigomega(k)==2, print1(n2-k, ", "); break))) \\ Hugo Pfoertner, Dec 06 2021
(Python)
from itertools import count
from sympy import factorint
def A349809(n):
    for i in count(n**2-(n%2)-1, -2):
        fs = factorint(i)
        if len(fs) == 2 == sum(fs.values()):
            return n**2-i # Chai Wah Wu, Dec 06 2021

Crossrefs

Cf. A099611.

Sequence in context: A185676 A277583 A213765 * A182971 A062145 A178216

Adjacent sequences: A349806 A349807 A349808 * A349810 A349811 A349812

Keyword

nonn

Author

N. J. A. Sloane, Dec 06 2021

Status

approved