A046380 Palindromes with exactly 6 palindromic prime factors (counted with multiplicity).

2772, 6776, 25452, 59895, 88788, 549945, 1931391, 8117118, 8447448, 51033015, 52711725, 58344385, 103838301, 535707535, 620434026, 1663223661, 8262112628, 15271417251, 25227972252, 27747974772, 27974547972, 92628082629, 97079897079, 6421339331246, 8401825281048

Offset: 1

Author

Patrick De Geest, Jun 15 1998

Keywords

• nonn
• base

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..49

Crossrefs

Cf. A046332.

Programs

Python

from sympy import factorint
def palQgen10(l): # generator of palindromes in base 10 of length <= 2*l
    if l > 0:
        yield 0
        for x in range(1,l+1):
            for y in range(10**(x-1),10**x):
                s = str(y)
                yield int(s+s[-2::-1])
            for y in range(10**(x-1),10**x):
                s = str(y)
                yield int(s+s[::-1])
A046380_list = []
for x in palQgen10(6):
    a = factorint(x)
    if sum(list(a.values())) == 6:
        for p in a:
            s = str(p)
            if s != s[::-1]:
                break
        else:
            A046380_list.append(x) # Chai Wah Wu, Dec 26 2014

Extensions

a(19)-a(25) from Chai Wah Wu, Dec 26 2014