A257652 The semiprimes which set new records for the sum of their decimal digits.
4, 6, 9, 38, 39, 49, 69, 169, 278, 289, 299, 489, 589, 689, 699, 799, 899, 2899, 3899, 4989, 5899, 5999, 6999, 7999, 9899, 19999, 29999, 48999, 58999, 68999, 69999, 88999, 99899, 299899, 398999, 589989, 589999, 689999, 798999, 889999, 899999, 2899999, 3899999
Offset: 1
Examples
a(4) = 38 = 2 * 19, which is a semiprime with sum of digits = 3 + 8 = 11. a(5) = 39 = 3 * 13, which is a semiprime with sum of digits = 3 + 9 = 12. Since 12 > 11, 38 and 39 are in list.
Links
- K. D. Bajpai, Table of n, a(n) for n = 1..64
Programs
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Mathematica
t = {}; s = 0; Do[If[(x = Total[IntegerDigits[n]]) > s && PrimeOmega[n] == 2, AppendTo[t, n]; s = x], {n, 1000000}];t DeleteDuplicates[{#,Total[IntegerDigits[#]]}&/@Select[Range[4*10^6],PrimeOmega[#] == 2&],GreaterEqual[ #1[[2]],#2[[2]]]&][[;;,1]] (* Harvey P. Dale, Apr 12 2024 *)
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