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 A327749 Natural numbers whose sum of prime factors (with repetition) is palindromic in base 10. 1
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 18, 20, 24, 27, 28, 40, 45, 48, 54, 57, 62, 85, 101, 102, 106, 116, 121, 123, 131, 151, 181, 182, 191, 194, 218, 259, 260, 278, 292, 298, 305, 308, 312, 313, 351, 353, 358, 366, 370, 373, 383, 388, 403, 413, 415, 428, 440, 444, 483, 495, 498 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Union of 1, A046352 and the palindromic primes (A002385). - Corrected by Robert Israel, Nov 20 2020 REFERENCES Karl G. Kröber, "Palindrome, Perioden und Chaoten: 66 Streifzüge durch die palindromischen Gefilde" (1997, Deutsch-Taschenbücher; Bd. 99) ISBN 3-8171-1522-9. Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 71. LINKS Robert Israel, Table of n, a(n) for n = 1..10000 MAPLE ispali:= proc(n) option remember; local L; L:= convert(n, base, 10); evalb(L = ListTools:-Reverse(L)) end proc: spf:= proc(n) add(t[1]*t[2], t=ifactors(n)[2]) end proc: select(t -> ispali(spf(t)), [\$0..1000]); # Robert Israel, Nov 20 2020 MATHEMATICA sopfr[1] = 0; sopfr[n_] := Plus @@ (Times @@@ FactorInteger[n]); aQ[n_] := PalindromeQ[sopfr[n]]; Select[Range[500], aQ] (* Amiram Eldar, Sep 23 2019 *) PROG (PARI) sopfr(n) = (n=factor(n))[, 1]~*n[, 2]; \\ A001414 isok(n) = my(d=digits(sopfr(n))); d == Vecrev(d); \\ Michel Marcus, Sep 27 2019 (Magma) [1] cat [k: k in [2..500]| Intseq(a) eq Reverse(Intseq(a)) where a is &+[m[1]*m[2]: m in Factorization(k)]]; // Marius A. Burtea, Sep 27 2019 CROSSREFS Cf. A001414, A002113, A002385, A046352, A046355. Sequence in context: A338883 A055722 A028830 * A171828 A246450 A049814 Adjacent sequences: A327746 A327747 A327748 * A327750 A327751 A327752 KEYWORD nonn,base AUTHOR Robert Bilinski, Sep 23 2019 STATUS approved

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Last modified August 3 19:15 EDT 2024. Contains 374903 sequences. (Running on oeis4.)