A046353 Odd composite numbers whose sum of prime factors is palindromic (counted with multiplicity).

9, 15, 27, 45, 57, 85, 121, 123, 259, 305, 351, 403, 413, 415, 483, 495, 575, 597, 627, 639, 663, 687, 689, 705, 717, 735, 807, 875, 893, 931, 935, 985, 989, 1073, 1135, 1183, 1203, 1207, 1263, 1285, 1293, 1331, 1353, 1383, 1385, 1407, 1473, 1505, 1545

Offset

1,1

Links

John Cerkan, Table of n, a(n) for n = 1..10000

Example

689 = 13 * 53 -> 13 + 53 = 66 and 66 is a palindrome.

Mathematica

palQ[n_]:=Reverse[x=IntegerDigits[n]]==x; Select[Range[9, 1545, 2], !PrimeQ[#]&&palQ[Total[Times@@@FactorInteger[#]]]&] (* Jayanta Basu, Jun 05 2013 *)

Prog

(Python)
from sympy import factorint
def is_046353(n):
    if n % 2 == 0: return False
    f = factorint(n)
    if sum([f[i] for i in f]) < 2: return False
    sfa = sum([i*f[i] for i in f])
    if sfa == int(str(sfa)[::-1]): return True
    return False # John Cerkan, Apr 24 2018

Crossrefs

Cf. A046352, A046354.

Sequence in context: A164385 A339519 A258813 * A340095 A046356 A248381

Adjacent sequences: A046350 A046351 A046352 * A046354 A046355 A046356

Keyword

nonn,base

Author

Patrick De Geest, Jun 15 1998

Extensions

Name clarified and offset changed by John Cerkan, Apr 24 2018

Status

approved