|
|
A332115
|
|
a(n) = (10^(2n+1)-1)/9 + 4*10^n.
|
|
6
|
|
|
5, 151, 11511, 1115111, 111151111, 11111511111, 1111115111111, 111111151111111, 11111111511111111, 1111111115111111111, 111111111151111111111, 11111111111511111111111, 1111111111115111111111111, 111111111111151111111111111, 11111111111111511111111111111, 1111111111111115111111111111111
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,1
|
|
COMMENTS
|
See A107125 = {0, 1, 7, 45, 115, 681, 1248, ...} for the indices of primes.
|
|
LINKS
|
|
|
FORMULA
|
G.f.: (5 - 404*x + 300*x^2)/((1 - x)(1 - 10*x)(1 - 100*x)).
a(n) = 111*a(n-1) - 1110*a(n-2) + 1000*a(n-3) for n > 2.
|
|
MAPLE
|
A332115 := n -> (10^(2*n+1)-1)/9+4*10^n;
|
|
MATHEMATICA
|
Array[(10^(2 # + 1)-1)/9 + 4*10^# &, 15, 0]
|
|
PROG
|
(PARI) apply( {A332115(n)=10^(n*2+1)\9+4*10^n}, [0..15])
(Python) def A332115(n): return 10**(n*2+1)//9+4*10**n
|
|
CROSSREFS
|
Cf. A138148 (cyclops numbers with binary digits), A002113 (palindromes).
Cf. A332125 .. A332195 (variants with different repeated digit 2, ..., 9).
Cf. A332112 .. A332119 (variants with different middle digit 2, ..., 9).
|
|
KEYWORD
|
nonn,base,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|