cp's OEIS Frontend

A072428 Numbers n for which there are exactly four k such that n = k + reverse(k).

%I A072428 #9 Jul 12 2019 20:18:29
%S A072428 44,165,404,424,444,464,484,504,524,544,564,584,1331,1515,1535,1555,
%T A072428 1575,1595,1615,1635,1655,1675,1695,2112,2651,3872,4004,5984,13031,
%U A072428 13231,13431,13631,13831,14031,14231,14431,14631,14831,15015,16995
%N A072428 Numbers n for which there are exactly four k such that n = k + reverse(k).
%C A072428 Subsequence of A067030. First term is A072041(4).
%C A072428 Includes 4*(10^k+1) for k>=1. - _Robert Israel_, Jul 12 2019
%H A072428 Robert Israel, <a href="/A072428/b072428.txt">Table of n, a(n) for n = 1..441</a>
%H A072428 <a href="/index/Res#RAA">Index entries for sequences related to Reverse and Add!</a>
%e A072428 44 = k + reverse(k) for k = 13, 22, 31, 40; 1331 = k + reverse(k) for k = 1030, 1120, 1210, 1300.
%p A072428 N:= 10^5:
%p A072428 revdigs:= proc(n) local L, i;
%p A072428   L:= convert(n, base, 10);
%p A072428   add(L[-i]*10^(i-1), i=1..nops(L))
%p A072428 end proc:
%p A072428 V:= Vector(N):
%p A072428 for x from 1 to N do
%p A072428   v:= x + revdigs(x);
%p A072428   if v <= N then V[v]:= V[v]+1 fi;
%p A072428 od:
%p A072428 select(t -> V[t]=4, [$1..N]); # Robert Israel, Jul 12 2019
%o A072428 (ARIBAS) var n,k,c,i,rev: integer; st,nst: string; end; m := 4; for n := 0 to 20000 do k := n div 2; c := 0; while k <= n and c < m + 1 do st := itoa(k); nst := ""; for i := 0 to length(st) - 1 do nst := concat(st[i],nst); end; rev := atoi(nst); if n = k + rev then inc(c); if k mod 10 <> 0 and k <> rev then inc(c); end; end; inc(k); end; if c = m then write(n,","); end; end;
%Y A072428 Cf. A067030, A072041.
%K A072428 base,nonn
%O A072428 1,1
%A A072428 _Klaus Brockhaus_, Jun 17 2002
%E A072428 Offset changed by _Robert Israel_, Jul 12 2019