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A073879 a(1) = 1, a(n) = smallest number not included earlier such that a(1)+...+a(n) is a palindrome. 3

%I

%S 1,2,3,5,11,22,33,24,10,20,30,41,40,50,21,60,31,70,51,81,80,61,71,91,

%T 90,112,110,220,330,231,440,550,121,660,341,770,451,671,880,561,781,

%U 891,882,100,200,300,410,400,500,210,600,310,700,510,810,800,610,710,910

%N a(1) = 1, a(n) = smallest number not included earlier such that a(1)+...+a(n) is a palindrome.

%H Ivan Neretin, <a href="/A073879/b073879.txt">Table of n, a(n) for n = 1..8323</a> (all terms before the sum exceeds 10^12)

%t seq={1}; Do[s=Total[seq]; k=1; While[MemberQ[seq, k] || !PalindromeQ[s+k], k++]; AppendTo[seq, k], {i,1,50}]; seq (* _Amiram Eldar_, Dec 04 2018 *)

%o (PARI)

%o ispal(n)={my(v=digits(n));for(i=1, #v\2, if(v[i]<>v[#v+1-i], return(0))); 1}

%o seq(n)={my(v=vector(n), M=Map(), t=0); for(n=1, n, for(k=1, oo, if(!mapisdefined(M,k) && ispal(k+t), mapput(M,k,1); v[n]=k; t+=k; break))); v} \\ _Andrew Howroyd_, Dec 04 2018

%Y Cf. A073880.

%K base,nonn,look

%O 1,2

%A _Amarnath Murthy_, Aug 16 2002

%E More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Jun 24 2003

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Last modified November 26 11:47 EST 2022. Contains 358359 sequences. (Running on oeis4.)