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A230020 Composite numbers n such that sigma(n) - reversal(n) = 1. 2
9599, 31874, 93689, 932639, 1367991, 13451831, 309173753, 99148830299 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
It is obvious that palindromic primes (palprimes) are all prime solutions of the equation sigma(x)-reversal(x) = 1. The next term is greater than 73*10^7.
a(9) > 10^12. - Giovanni Resta, Dec 14 2013
LINKS
EXAMPLE
sigma(9599) = sigma(29*331) = 30*332 = 9960 = reverse(9599)+1.
MATHEMATICA
Do[a=FromDigits[Reverse[IntegerDigits[n]]]; If[a>n && DivisorSigma[1, n] -a == 1, Print[n]], {n, 730000000}]
CROSSREFS
Sequence in context: A250761 A038825 A038814 * A034626 A031596 A236715
KEYWORD
nonn,base,more
AUTHOR
Farideh Firoozbakht, Nov 26 2013
EXTENSIONS
a(8) from Giovanni Resta, Dec 14 2013
STATUS
approved

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Last modified May 20 19:00 EDT 2024. Contains 372720 sequences. (Running on oeis4.)