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%I #7 Feb 23 2019 22:11:31
%S 2,11,13,17,31,53,71,79,97,101,103,107,211,233,251,277,349,367,431,
%T 439,457,503,521,547,619,673,691,701,709,727,853,907,1021,1061,1069,
%U 1087,1151,1201,1223,1249,1429,1447,1483,1511,1601,1609,1627,1663,1753,1861,1933,1951,2011,2099
%N 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.
%H Harvey P. Dale, <a href="/A178796/b178796.txt">Table of n, a(n) for n = 1..1000</a>
%e 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.
%p 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:
%p seq(A178796(n),n=1..80) ; # _R. J. Mathar_, Jun 28 2010
%t 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 *)
%Y Different from A068807.
%K base,nonn
%O 1,1
%A _Giovanni Teofilatto_, Jun 15 2010
%E Corrected by _Giovanni Teofilatto_, Jun 25 2010
%E Definition corrected, sequence extended, example added by _R. J. Mathar_, Jun 28 2010
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