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A174055
Sums of three Mersenne primes.
4
9, 13, 17, 21, 37, 41, 45, 65, 69, 93, 133, 137, 141, 161, 165, 189, 257, 261, 285, 381, 8197, 8201, 8205, 8225, 8229, 8253, 8321, 8325, 8349, 8445, 16385, 16389, 16413, 16509, 24573, 131077, 131081, 131085, 131105, 131109, 131133, 131201, 131205, 131229, 131325, 139265, 139269, 139293, 139389, 147453, 262145, 262149
OFFSET
1,1
LINKS
FORMULA
A000668(i) + A000668(j) + A000668(k), with integers i,j,k not necessarily distinct. The subsequence of prime sums of three Mersenne primes is A174056.
EXAMPLE
a(1) = 3 + 3 + 3 = 9. a(2) = 3 + 3 + 7 = 13. a(3) = 3 + 7 + 7 = 17. a(4) = 7 + 7 + 7 = 21. a(5) = 3 + 3 + 31 = 37. a(6) = 3 + 7 + 31 = 41.
MAPLE
N:= 10^6: # to get all terms <= N
for n from 1 while numtheory:-mersenne([n]) < N do od:
S:= {seq(numtheory:-mersenne([i]), i=1..n-1)}:
sort(convert(select(`<=`, {seq(seq(seq(s+t+u, s=S), t=S), u=S)}, N), list)); # Robert Israel, Mar 02 2016
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Mar 06 2010
EXTENSIONS
More terms from Max Alekseyev, Oct 15 2012
Edited by Robert Israel, Mar 02 2016
STATUS
approved