OFFSET
1,2
COMMENTS
Numbers n such that there is a unique subset S of the Mersenne exponents A000043 summing to n. - Charles R Greathouse IV, Mar 07 2017
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..168
FORMULA
A283446(a(n)) = 1.
EXAMPLE
8 is in this sequence that k = 217 is the only number having sigma(k) = 2^8.
PROG
(PARI) is(n)=my(N=2^n, s); for(k=1, N, if(sigma(k)==N && s++>1, return(0))); s \\ Charles R Greathouse IV, Mar 07 2017
(PARI) list(lim)=my(v=List(), M=[2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107, 127, 521, 607, 1279, 2203, 2281, 3217, 4253, 4423, 9689, 9941, 11213, 19937, 21701, 23209, 44497, 86243, 110503, 132049, 216091, 756839, 859433, 1257787, 1398269, 2976221, 3021377, 6972593, 13466917, 20996011, 24036583, 25964951, 30402457, 32582657, 37156667], x='x, P); if(lim>M[#M], error("Need more Mersenne exponents to compute further")); M=select(p->p<=lim, M); P=prod(i=1, #M, 1+x^M[i], O(x^(lim\1+1))+1); for(i=0, lim, if(polcoeff(P, i)==1, listput(v, i))); P=0; Vec(v) \\ Charles R Greathouse IV, Mar 07 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Mar 01 2017
EXTENSIONS
a(9)-a(55) from Charles R Greathouse IV, Mar 07 2017
STATUS
approved