|
| |
|
|
A143813
|
|
Sum of two powerful numbers.
|
|
2
| |
|
|
8, 12, 13, 16, 17, 18, 20, 24, 25, 29, 31, 32, 33, 34, 35, 36, 40, 41, 43, 44, 45, 48, 50, 52, 53, 54, 57, 58, 59, 61, 63, 64, 65, 68, 72, 73, 74, 76, 80, 81, 85, 88, 89, 90, 91, 96, 97, 98, 99, 100, 104, 106, 108, 109, 112, 113, 116, 117, 121, 124, 125, 127
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| A001694 + A001694.
The powerful numbers which are also the sum of two powerful numbers begin: 8, 16, 25, 32, 36, 64, 72, 81, 100, 108, 121, 125 [Jonathan Vos Post, July 9, 2011].
|
|
|
EXAMPLE
| 8 = 4 + 4, 12 = 4 + 8, 13 = 4 + 9.
|
|
|
PROG
| (PARI) isPowerful(n)={
n>3 && vecmin(factor(n)[, 2])>1
};
sumset(a, b)={
my(c=vector(#a*#b));
for(i=1, #a,
for(j=1, #b,
c[(i-1)*#b+j]=a[i]+b[j]
)
);
vecsort(c, , 8)
};
upto(lim)={
my(v=select(isPowerful, vector(floor(lim), i, i)));
select(n->n<=lim, sumset(v, v))
};
|
|
|
CROSSREFS
| Sequence in context: A160862 A152077 A173461 * A143845 A048868 A106669
Adjacent sequences: A143810 A143811 A143812 * A143814 A143815 A143816
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Charles R Greathouse IV (charles.greathouse(AT)case.edu), Jul 06 2011
|
| |
|
|
