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A185351
Sums of distinct perfect numbers.
3
0, 6, 28, 34, 496, 502, 524, 530, 8128, 8134, 8156, 8162, 8624, 8630, 8652, 8658, 33550336, 33550342, 33550364, 33550370, 33550832, 33550838, 33550860, 33550866, 33558464, 33558470, 33558492, 33558498, 33558960, 33558966, 33558988, 33558994, 8589869056
OFFSET
1,2
COMMENTS
The first 131072 terms of this sequence are even. Conjecturally, all terms are even.
Numbers in the range of the sum of perfect divisors function (A187794). - Timothy L. Tiffin, Jul 13 2016
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
502 = 496 + 6, where 496 and 6 are perfect.
MATHEMATICA
With[{perf = Select[Range[10000], DivisorSigma[1, #] == 2# &]}, Rest[Union[Total/@Subsets[perf]]]] (* Harvey P. Dale, Feb 07 2012 *)
PROG
(PARI) vecsum(v)=sum(i=1, #v, v[i]);
v=apply(n->binomial(n+1, 2), select(k->ispseudoprime(k), vector(15, n, 2^prime(n)-1))); u=List(); for(i=0, 2^#v-1, listput(u, vecsum(vecextract(v, i)))); vecsort(Vec(u)) \\ Charles R Greathouse IV, Feb 09 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved