|
| |
|
|
A260853
|
|
Base-3 representation of a(n) is the concatenation of the base-3 representations of 1, 2, ..., n, n-1, ..., 1.
|
|
21
|
|
|
|
0, 1, 16, 439, 35350, 2864599, 232046890, 18795930559, 1522471570630, 369960528437035, 269701223137448146, 196612191672080116867, 143330287729139571972130, 104487779754548024866115515, 76171591441065652665051372946, 55529090160536864641400481743827
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
0,3
|
|
|
COMMENTS
|
The base 3 is listed in A260343, which means that a(3) = A260851(3) = 439 = 121021_3 is prime and therefore in A260852. See these sequences for more information.
|
|
|
LINKS
|
Table of n, a(n) for n=0..15.
D. Broadhurst, Primes from concatenation: results and heuristics, NmbrThry List, August 1, 2015
Index entries for sequences related to Most Wanted Primes video
|
|
|
EXAMPLE
|
a(0) = 0 is the result of the empty sum corresponding to 0 digits.
a(2) = 16 = 121_3 is the concatenation of (1, 2, 1).
a(3) = 439 = 121021_3 is the concatenation of (1, 2, 10, 2, 1), where the middle "10" is the base-3 representation of 3.
|
|
|
MATHEMATICA
|
Join[{0}, Table[FromDigits[Join[Flatten[IntegerDigits[Range[n], 3]], Flatten[ Reverse[ Most[ IntegerDigits[Range[n], 3]]]]], 3], {n, 20}]] (* Harvey P. Dale, Mar 11 2019 *)
|
|
|
PROG
|
(PARI) a(n, b=3)=sum(i=1, #n=concat(vector(n*2-1, k, digits(min(k, n*2-k), b))), n[i]*b^(#n-i))
|
|
|
CROSSREFS
|
Base-3 variant of A173426 (base 10) and A173427 (base 2). See A260854 - A260866 for variants in other bases b = 4, ..., 16.
Sequence in context: A223686 A000489 A075852 * A068792 A229583 A241077
Adjacent sequences: A260850 A260851 A260852 * A260854 A260855 A260856
|
|
|
KEYWORD
|
nonn,base
|
|
|
AUTHOR
|
M. F. Hasler, Aug 01 2015
|
|
|
STATUS
|
approved
|
| |
|
|
