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A217690 Numbers n such that sum of digits of n equals the least prime dividing n and sum of squares of digits of n equals the greatest prime dividing n. 0
133, 803, 2023, 106811, 383177, 1071949, 1342027, 2025343, 2569757, 2911123, 3341831, 3993883, 6285901, 10860071, 11194319, 13270013, 21736109, 21871477, 22159451, 22421587, 26011229, 27600257, 31174391, 32656681, 34880611, 40435193, 41755573, 53738911 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..28.

FORMULA

k such that A020639(k) = A007953(k) and A006530(k) = A003132(k).

EXAMPLE

383177 = 29 * 73 * 181 is in the sequence because 29 = 3+8+3+1+7+7 and 181 = 3^2+8^2+3^2+1^2+7^2+7^2.

MAPLE

with(numtheory):A:= proc(n) add(u, u=convert(n, base, 10)) ; end proc: B:= proc(m) add(v^2, v=convert(m, base, 10)) ; end proc: for i from 2 to 1000000 do:x:=factorset(i):n1:=nops(x):if x[1]=A(i) and x[n1]=B(i) then print(i):else fi:od:

PROG

(PARI) is_A217690(n)={my(d=digits(n), s=norml2(d), f); (n%s || !isprime(s) || n%(d=sum(i=1, #d, d[i])) || !isprime(d)) & return; !(f=factor(n/(d*s))[, 1]) || (d <= f[1] & s >= f[#f])} \\ Charles R Greathouse IV and M. F. Hasler, Oct 11 2012

CROSSREFS

Cf. A007953, A003132, A020639, A006530.

Sequence in context: A137879 A249108 A020237 * A117565 A274175 A038491

Adjacent sequences:  A217687 A217688 A217689 * A217691 A217692 A217693

KEYWORD

nonn,base

AUTHOR

Michel Lagneau, Oct 11 2012

STATUS

approved

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Last modified December 9 07:21 EST 2021. Contains 349627 sequences. (Running on oeis4.)