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URL: https://oeis.org/A277217

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A277217
Numbers k for which the sum of digits of sigma(k) = the product of digits of sigma(k).
2
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 k such that A067342(k) = A277216(k).
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 k such that sigma(k) 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. 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
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Oct 05 2016
STATUS
approved