A081931 Diagonal of triangle in A081930.

1, 22, 121, 1331, 10401, 105501, 1006001, 10077001, 100080001, 1000990001, 10001010001

Offset

1,2

Links

Table of n, a(n) for n=1..11.

Maple

isA002113 := proc(n) local digrev, d ; digrev := convert(n, base, 10) ; for d from 1 to nops(digrev)/2 do if op(d, digrev) <> op(-d, digrev) then RETURN(false) ; fi ; od ; RETURN(true) ; end: A081930 := proc(n) local a, k ; a := [] ; k := 10^(n-1) ; while nops(a) < n do if isA002113(k) then a := [op(a), k] ; fi ; k := k+1 ; od ; RETURN(a) ; end: A081931 := proc(n) local nrow ; nrow := A081930(n) ; RETURN(op(-1, nrow)) ; end: for n from 1 to 18 do A081931(n) ; od ; # R. J. Mathar, Apr 04 2007

Crossrefs

Cf. A081930, A081932.

Sequence in context: A039612 A085828 A221698 * A156293 A225308 A043498

Adjacent sequences: A081928 A081929 A081930 * A081932 A081933 A081934

Keyword

base,more,nonn

Author

Amarnath Murthy, Apr 01 2003

Extensions

More terms from R. J. Mathar, Apr 04 2007

Status

approved