|
|
A332170
|
|
a(n) = 7*(10^(2n+1)-1)/9 - 7*10^n.
|
|
2
|
|
|
0, 707, 77077, 7770777, 777707777, 77777077777, 7777770777777, 777777707777777, 77777777077777777, 7777777770777777777, 777777777707777777777, 77777777777077777777777, 7777777777770777777777777, 777777777777707777777777777, 77777777777777077777777777777, 7777777777777770777777777777777
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
LINKS
|
|
|
FORMULA
|
G.f.: 7*x*(101 - 200*x)/((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
|
A332170 := n -> 7*(10^(2*n+1)-1)/9-7*10^n;
|
|
MATHEMATICA
|
Array[7 ((10^(2 # + 1)-1)/9 - 10^#) &, 15, 0]
|
|
PROG
|
(PARI) apply( {A332170(n)=(10^(n*2+1)\9-10^n)*7}, [0..15])
(Python) def A332170(n): return (10**(n*2+1)//9-10^n)*7
|
|
CROSSREFS
|
Cf. A138148 (cyclops numbers with binary digits only), A002113 (palindromes).
Cf. A332120 .. A332190 (variants with different repeated digit 2, ..., 9).
Cf. A332171 .. A332179 (variants with different middle digit 1, ..., 9).
|
|
KEYWORD
|
nonn,base,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|