|
| |
|
|
A119730
|
|
Primes p such that p+1, p+2, p+3, p+4 and p+5 have equal number of divisors.
|
|
4
|
|
|
|
13781, 19141, 21493, 50581, 142453, 152629, 253013, 298693, 307253, 346501, 507781, 543061, 845381, 1079093, 1273781, 1354501, 1386901, 1492069, 1546261, 1661333, 1665061, 1841141, 2192933, 2208517, 2436341, 2453141, 2545013
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
LINKS
|
Amiram Eldar, Table of n, a(n) for n = 1..10000
|
|
|
EXAMPLE
|
13781 is a term since 13782, 13783, 13784, 13785 and 13786 all have 8 divisors:
{1,2,3,6,2297,4594,6891,13782}, {1,7,11,77,179,1253,1969,13783},
{1,2,4,8,1723,3446,6892,13784}, {1,3,5,15,919,2757,4595,13785} and
{1,2,61,113,122,226,6893,13786}.
|
|
|
MATHEMATICA
|
Select[Prime@Range[1000000], DivisorSigma[0, #+1]==DivisorSigma[0, #+2]==DivisorSigma[0, #+3]==DivisorSigma[0, #+4]==DivisorSigma[0, #+5]&]
endQ[n_]:= Length[Union[DivisorSigma[0, (n + Range[5])]]]==1; Select[Prime[ Range[ 200000]], endQ] (* Harvey P. Dale, Jan 16 2019 *)
|
|
|
CROSSREFS
|
Cf. A008329, A049234, A119705, A119711, A119728, A119740.
Sequence in context: A235184 A270639 A031807 * A204839 A208487 A188102
Adjacent sequences: A119727 A119728 A119729 * A119731 A119732 A119733
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Zak Seidov, Jul 29 2006
|
|
|
STATUS
|
approved
|
| |
|
|
