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A082935
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Smallest palindrome beginning with n and a digit sum of n at some stage.
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0
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1, 2, 3, 4, 5, 6, 7, 8, 9, 10801, 11711, 12621, 13531, 14441, 15351, 16261, 17171, 1881, 1949999999999999999999491, 208802, 2139312, 227722, 2329232, 246642, 2519152, 265562, 27972, 28882, 29792, 3088803, 3179713, 3278723, 3369633, 3468643
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OFFSET
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1,2
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COMMENTS
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In most cases (perhaps in all other) except for n = 19 the digit sum in the first round itself is n. In case of 19 the first round of digit sum is 199 and the second round digit sum is 19.
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LINKS
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EXAMPLE
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a(19)=1949999999999999999999491. The smallest such number is 194 followed by 19 nines followed by 491. The first digit sum would be 199 and the next sum is 19.
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MATHEMATICA
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(*This code works for all numbers up to 100 except 19*) NextPalindrome[n_] := Block[{l = Floor[Log[10, n] + 1], idn = IntegerDigits[n]}, If[ Union[idn] == {9}, Return[n + 2], If[l < 2, Return[n + 1], If[ FromDigits[ Reverse[ Take[idn, Ceiling[l/2]]]] FromDigits[ Take[idn, -Ceiling[l/2]]], FromDigits[ Join[ Take[idn, Ceiling[l/2]], Reverse[ Take[idn, Floor[l/2]]]]], idfhn = FromDigits[ Take[idn, Ceiling[l/2]]] + 1;
idp = FromDigits[ Join[ IntegerDigits[idfhn], Drop[ Reverse[ IntegerDigits[ idfhn]], Mod[l, 2]]]]]]]]; f[n_] := Block[{k = 1, dn = IntegerDigits[n]}, sdn = 2*Plus @@ dn; If[sdn == 2n, n, If[sdn == n, FromDigits[ Join[dn, Reverse[dn]]], If[sdn > n, 0, k = 10^Floor[(n - sdn)/9] - 1;; While[Plus @@ IntegerDigits[k] + sdn != n, k = NextPalindrome[k]]; FromDigits[ Join[dn, IntegerDigits[k], Reverse[dn]]]]]]]; Table[ f[n], {n, 1, 35}]
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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Meenakshi Srikanth (menakan_s(AT)yahoo.com), Apr 16 2003
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EXTENSIONS
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STATUS
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approved
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