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A277217 Numbers n for which the sum of digits of sigma(n) = the product of digits of sigma(n). 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 (list; graph; refs; listen; history; text; internal format)
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 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

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Last modified August 14 09:14 EDT 2020. Contains 336480 sequences. (Running on oeis4.)