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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).
2
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
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
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, May 20 2002
EXTENSIONS
More terms from James A. Sellers, May 28 2002
STATUS
approved