A071240 Arithmetic mean of k and R(k) where k is a number using only odd digits and R(k) is its digit reversal (A004086).

1, 3, 5, 7, 9, 11, 22, 33, 44, 55, 22, 33, 44, 55, 66, 33, 44, 55, 66, 77, 44, 55, 66, 77, 88, 55, 66, 77, 88, 99, 111, 212, 313, 414, 515, 131, 232, 333, 434, 535, 151, 252, 353, 454, 555, 171, 272, 373, 474, 575, 191, 292, 393, 494, 595, 212, 313, 414, 515, 616

Offset

0,2

Links

Table of n, a(n) for n=0..59.

Formula

{k + R(k)}/2 where k uses only odd digits 1, 3, 5, 7 and 9.

a(n) = (A014261(n) + A004086(A014261(n))) / 2. - Sean A. Irvine, Jul 06 2024

Maple

reversal := proc(n) local i, len, new, temp:
    new := 0: temp := n: len := floor(log[10](n+.1))+1:
    for i from 1 to len do
        new := new+irem(temp, 10)*10^(len-i):
        temp := floor(temp/10):
    od:
    RETURN(new):
end:
allodd := proc(n) local i, flag, len, temp:
    temp := n: flag := 1: if n=0 then flag := 0 fi: len := floor(log[10](n+.1))+1:
    for i from 1 to len do
        if irem(temp, 10) mod 2 = 1 then temp := floor(temp/10) else flag := 0 fi:
    od:
    RETURN(flag):
end:
for n from 1 to 501 by 2 do
    if allodd(n) = 1 then printf(`%d, `, (n+reversal(n))/2) fi:
od: # James A. Sellers, May 28 2002

Crossrefs

Cf. A004086, A014261, A071241, A071242.

Sequence in context: A211138 A178995 A346604 * A088049 A229364 A029660

Adjacent sequences: A071237 A071238 A071239 * A071241 A071242 A071243

Keyword

base,nonn

Author

Amarnath Murthy, May 20 2002

Extensions

More terms from James A. Sellers, May 28 2002

Status

approved