|
| |
|
|
A109870
|
|
Number of ways a number can be expressed as the arithmetic mean of two palindromes.
|
|
2
| |
|
|
1, 2, 3, 4, 4, 4, 3, 2, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 0, 1, 2, 2, 2, 2, 5, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 5, 2, 1, 1, 1, 2, 2, 1, 1, 1, 2, 4, 2, 1, 1, 2, 2, 2, 1, 1, 2, 2, 3, 2, 1, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
EXAMPLE
| a(5)=4 because 5=(4+6)/2=(3+7)/2=(2+8)/2=(1+9)/2. a(17)=1 because 17=(1+33)/2. a(18)=1 because 18=(3+33)/2.
|
|
|
MAPLE
| isA002113 := proc(n) option remember ; local digs, i ; digs := convert(n, base, 10) ; for i from 1 to nops(digs)/2 do if op(i, digs) <> op(-i, digs) then RETURN(false) ; fi ; od: RETURN(true) ; end: A109870 := proc(n) local a, d ; a := 0 ; for d from n-1 to 0 by -1 do if isA002113(d) and isA002113(2*n-d) then a := a+1 ; fi ; od: RETURN(a) ; end: seq(A109870(n), n=1..120) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 15 2007
|
|
|
CROSSREFS
| Cf. A109871.
Sequence in context: A101083 A097935 A188940 * A171502 A005102 A030241
Adjacent sequences: A109867 A109868 A109869 * A109871 A109872 A109873
|
|
|
KEYWORD
| base,nonn
|
|
|
AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 09 2005
|
|
|
EXTENSIONS
| Corrected and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 15 2007
|
| |
|
|
