|
|
A039832
|
|
Numbers k such that k and k+1 both have 4 divisors.
|
|
8
|
|
|
14, 21, 26, 33, 34, 38, 57, 85, 86, 93, 94, 118, 122, 133, 141, 142, 145, 158, 177, 201, 202, 205, 213, 214, 217, 218, 253, 298, 301, 302, 326, 334, 381, 393, 394, 445, 446, 453, 481, 501, 514, 526, 537, 542, 553, 565, 622, 633, 634, 694, 697, 698, 706, 717, 745, 766, 778, 793, 802, 817
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
REFERENCES
|
David Wells, Curious and interesting numbers, Penguin Books, 1986, p. 91.
|
|
LINKS
|
|
|
EXAMPLE
|
14 and 15 both have 4 as number of divisors and are consecutive.
|
|
MATHEMATICA
|
Flatten[Position[Partition[Table[DivisorSigma[0, n], {n, 1000}], 2, 1], _?(#=={4, 4}&)]] (* Vincenzo Librandi, Oct 21 2012 *)
|
|
PROG
|
(PARI) isA039832(n) = numdiv(n)==4 && numdiv(n+1)==4 \\ Michael B. Porter, Feb 03 2010
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|