OFFSET
1,2
COMMENTS
Sequence is infinite; it includes all powers of 4. More generally, if n is in this sequence, let i be the number just added to make the sum equal to n. If i+1 is divisible by every prime divisor of n, then n*m^2 is in the sequence for any number m whose prime divisors all divide n. This gives us subsequences 3*9^i, 6*4^i*9^j, 20*4^i*25^j, 120*4^i*9^j*25^k, etc. - Franklin T. Adams-Watters, Dec 18 2006
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..2000
EXAMPLE
6 is a member as 6 = 1 + 5. 16 is also a member.
The numbers coprime to 16 are 1, 3, 5, 7, 9, 11, 13, 15. The partial sums are 1, 4, 9, 16, 25,...
MATHEMATICA
seqQ[n_] := MemberQ[Accumulate @ Select[Range[n], CoprimeQ[n, #] &], n]; Select[Range[3500], seqQ] (* Amiram Eldar, Feb 23 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Mar 22 2004
EXTENSIONS
More terms from Franklin T. Adams-Watters, Dec 18 2006
STATUS
approved