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A178796
An ascending sequence of primes a(n) such that either the sum of decimal digits of a(n) is divisible by the sum of decimal digits of a(n+1) or vice versa.
3
2, 11, 13, 17, 31, 53, 71, 79, 97, 101, 103, 107, 211, 233, 251, 277, 349, 367, 431, 439, 457, 503, 521, 547, 619, 673, 691, 701, 709, 727, 853, 907, 1021, 1061, 1069, 1087, 1151, 1201, 1223, 1249, 1429, 1447, 1483, 1511, 1601, 1609, 1627, 1663, 1753, 1861, 1933, 1951, 2011, 2099
OFFSET
1,1
LINKS
EXAMPLE
The sums of the digits of a(n) form the sequence d(n) = 2, 2, 4, 8, 4, 8, 8, 16, ... in which either d(n)/d(n+1) or d(n+1)/d(n) is an integer.
MAPLE
A178796 := proc(n) option remember; if n = 1 then 2; else a := nextprime(procname(n-1)) ; while true do r := A007953(a)/ A007953(procname(n-1)) ; if numer(r) = 1 or denom(r) = 1 then return a; end if; a := nextprime(a) ; end do: end if; end proc:
seq(A178796(n), n=1..80) ; # R. J. Mathar, Jun 28 2010
MATHEMATICA
nxt[n_]:=Module[{k=NextPrime[n], tidn=Total[IntegerDigits[n]]}, While[ !Divisible[ Total[ IntegerDigits[ k]], tidn] && !Divisible[ tidn, Total[ IntegerDigits[k]]], k=NextPrime[k]]; k]; NestList[nxt, 2, 60] (* Harvey P. Dale, Aug 23 2017 *)
CROSSREFS
Different from A068807.
Sequence in context: A079132 A184802 A023257 * A068807 A241732 A154812
KEYWORD
base,nonn
AUTHOR
Giovanni Teofilatto, Jun 15 2010
EXTENSIONS
Corrected by Giovanni Teofilatto, Jun 25 2010
Definition corrected, sequence extended, example added by R. J. Mathar, Jun 28 2010
STATUS
approved