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A046453

Composite numbers with four prime factors (not necessarily distinct) whose concatenation yields a palindrome.

16, 81, 625, 2401, 3975, 4719, 5565, 6591, 8745, 10731, 14399, 14641, 16863, 20111, 34391, 36501, 39963, 41019, 46179, 47229, 48231, 60813, 61761, 62991, 69027, 109179, 113631, 116475, 143991, 158985, 159777, 162409, 164145, 167571, 183159, 184065

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..36.

EXAMPLE

164145 = 3 * 5 * 31 * 353 -> 3531353 is palindromic.

MATHEMATICA

pal4Q[n_]:=Module[{ds=Flatten[IntegerDigits/@(Table[First[#], {Last[ #]}]&/@ FactorInteger[n])]}, PrimeOmega[n]==4&&ds==Reverse[ds]]; Select[ Range[190000], pal4Q] (* Harvey P. Dale, Nov 12 2011 *)

CROSSREFS

Intersection of A033993 and A046447.

Sequence in context: A369168 A366307 A113849 * A030514 A056571 A053909

Adjacent sequences: A046450 A046451 A046452 * A046454 A046455 A046456

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Jul 15 1998

EXTENSIONS

One more term from Harvey P. Dale, Nov 12 2011

STATUS

approved

URL: https://oeis.org/A046453

⇱ A046453 - OEIS