A277217 Numbers n for which the sum of digits of sigma(n) = the product of digits of sigma(n).

1, 2, 3, 4, 5, 7, 86, 126, 131, 206, 207, 311, 1123, 1213, 2113, 4111, 10921, 12211, 16581, 21121, 21211, 22111, 39660, 51558, 52940, 60812, 61504, 63548, 68822, 81303, 83409, 87081, 87451, 89708, 94523, 97307, 106118, 108527, 110387, 111611, 120831, 160271

Offset

1,2

Comments

Numbers n such that A067342(n) = A277216(n).

Prime terms: 2, 3, 5, 7, 131, 311, 1123, 1213, 2113, 4111, 12211, ...

Corresponding values of sigma(a(n)): 1, 3, 4, 7, 6, 8, 132, 312, 132, 312, 312, 312, 1124, 1214, 2114, ...

Only 196 terms less than 35*10^8. - Robert G. Wilson v, Oct 07 2016

Alternatively, numbers n such that sigma(n) is in A034710. - Charlie Neder, Dec 27 2018

Links

Robert G. Wilson v, Table of n, a(n) for n = 1..196 (first 100 terms from Jaroslav Krizek)

Example

86 is a term because sigma(86) = 132; sum and product of digits of 132 = 6.

Mathematica

Select[Range@ 200000, Total@ # == Times @@ # &@ IntegerDigits@ DivisorSigma[1, #] &] (* Michael De Vlieger, Oct 06 2016 *)

Prog

(Magma) [n: n in [1..100000] | &+Intseq(SumOfDivisors(n)) eq &*Intseq(SumOfDivisors(n))]
(PARI) isok(n) = my(d=digits(sigma(n))); vecprod(d) == vecsum(d); \\ Michel Marcus, Mar 02 2019

Crossrefs

Cf. A000203, A007953, A007954, A034710.

Cf. A067342 (sum of decimal digits of sigma(n)), A277216 (product of decimal digits of sigma(n)).

Sequence in context: A096841 A029963 A259389 * A259384 A285888 A028986

Adjacent sequences: A277214 A277215 A277216 * A277218 A277219 A277220

Keyword

nonn,base

Author

Jaroslav Krizek, Oct 05 2016

Status

approved