This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
Starting with 26, 3 Reverse and Add! steps are needed to reach a palindrome; starting with n < 26, less (at most 2) steps are needed.
Starting with 26, 3 Reverse and Add! steps are needed to reach a palindrome; starting with n < 26, less (at most 2) steps are needed.
17 (decimal) = 122 -> 122 + 221 = 1120 -> 1120 + 211 = 2101 -> 2101 + 1012 = 10120 -> 10120 + 2101 = 12221 (palindrome) = 160 (decimal) requires 4 steps, so a(17) = 4.
m := 120; stop := 1000; for n := 0 to m do v := -1; c := 0; k := n; while c < stop do d := k; rev := 0; while d > 0 do rev := 3*rev + (d mod 3); d := d div 3; end; if k = rev then v := c; c := stop; else inc(c); k := k + rev; end; end; write(v,","); end;
7 is the smallest number which requires two steps to reach a base 4 palindrome (cf. A075685), so a(2) = 5; 7 (decimal) = 13 -> 13 + 31 = 110 -> 110 + 011 = 121 (palindrome) = 25 (decimal).
{m=46; v=[]; for(j=1,m+1,v=concat(v,-1)); mc=m+1; n=0; while(mc>0,a=-1; c=0; k=n; while(c0,d=divrem(q,4); q=d[1]; rev=4*rev+d[2]); if(k==rev,a=c; c=m+1,c++; k=k+rev)); if(0<=a&&a<=m,if(v[a+1]<0,v[a+1]=n; mc--; print1([a,n]))); n++); print(); for(j=1,m+1,print1(v[j],","))}
from gmpy2 import digits def A077441(n): if n > 0: k = 0 while True: m = k for i in range(n): s = digits(m,4) if s == s[::-1]: break m += int(s[::-1],4) else: s = digits(m,4) if s == s[::-1]: return k k += 1 else: return 0 # Chai Wah Wu, Jan 17 2015
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