Voozh

A317670

Numbers k such that sigma_0(k-1) + sigma_0(k) + sigma_0(k+1) = 10, where sigma_0(k) = A000005(k).

7, 12, 14, 18, 22, 38, 58, 158, 178, 382, 502, 542, 718, 878, 1202, 1318, 1382, 1438, 1622, 1822, 2018, 2558, 2578, 2858, 2902, 3062, 3118, 3778, 4282, 4358, 4442, 4678, 4702, 5078, 5098, 5582, 5638, 5702, 5938, 6338, 6638, 6662, 6718, 6998, 7418, 8222, 8782, 8818, 9182, 9662, 9902

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Besides the 1st, 2nd, and 4th terms, a(n) is 2 times a prime, one of a(n)-1 or a(n)+1 is a prime, and the other number is 3 times a prime.

The 10 in the definition is the smallest value for which this is a possibly infinite list.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

For a(3)=14, sigma_0(13)=2, sigma_0(14)=4, and sigma_0(15)=4, hence sigma_0(a(3)-1) + sigma_0(a(3)) + sigma_0(a(3)+1) = 10.

MAPLE

Res:= 7, 12, 14, 18: count:= 4: