A178321 -id:A178321 - cp's OEIS frontend

A072394 Numbers n such that sigma(n)=reversal(n)-n.

1563, 1633, 18673, 32207, 1405313, 1567563, 1656833, 193613415, 325933027, 376491249, 2287850446, 2432416646, 13823276223, 14055445313, 19087920283, 23804849568, 36303512827, 148868530953

Offset: 1

Joseph L. Pe, Jul 21 2002

If (58*1000^n-169)/111 is prime then (58*1000^n-169)/37 is in the sequence (the proof is easy). Next term is greater than 12*10^8. - Farideh Firoozbakht, Jan 29 2006
From Farideh Firoozbakht, May 25 2010: (Start)
If p = 156/101*(10^(4n)-1)-1 is prime then 91*p is in the sequence (the proof is easy).
A178321 gives numbers n such that (58*1000^n-169)/111 = 58/111*(10^(3n)-1)-1 is prime and A178322 gives numbers n such that 156/101*(10^(4n)-1)-1 is prime. (End)
a(19) > 10^12. - Giovanni Resta, Oct 28 2012

			reverse(1563) - 1563 = 3651 - 1563 = 2088 = sigma(1563), so 1563 is a term of the sequence.
376491249 is in the sequence because sigma(376491249)=565703424 =942194673-376491249=reversal(376491249)-376491249.

Cf. A072234.

Cf. A178321, A178322. [From Farideh Firoozbakht, May 25 2010]

Select[Range[10^6], FromDigits[Reverse[IntegerDigits[n]]] - # == DivisorSigma[1, # ] &]
Do[If[DivisorSigma[1,n]==FromDigits[Reverse[IntegerDigits[n]]]- n,Print[n]],{n,1200000000}] (* Farideh Firoozbakht *)

More terms from Farideh Firoozbakht, Jan 29 2006
a(11)-a(17) from Donovan Johnson, Dec 21 2008
a(18) from Giovanni Resta, Oct 28 2012

A178322 Numbers n such that 156/101*(10^(4n)-1)-1 is prime.

Original entry on oeis.org

1, 2, 5, 29, 30, 108, 679, 4478, 8736, 17000, 22427, 22731

Offset: 1

Farideh Firoozbakht, May 26 2010

If n is in the sequence then m=91*(156/101*(10^(4n)-1)-1) is a term of A072394. Namely if n is a term of this sequence then for m=1/101*(14196*10^(4n)-23387), we have sigma(m)=reversal(m)-m (see comment lines of A072394).
Numbers corresponding to the larger terms are probable primes.
Next term exceeds 3500. - Robert G. Wilson v, Aug 08 2011.
a(13) > 40000. - Robert Price, May 23 2014

Cf. A072394, A178321.

Select[Range[700], PrimeQ[156/101*(10^(4 #) - 1) - 1] &]

a(8)-a(12) from Robert Price, May 23 2014

cp's OEIS Frontend

A072394 Numbers n such that sigma(n)=reversal(n)-n.

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