A092595 - OEIS

%I #38 Dec 20 2021 21:02:09

%S 2,11,20,29,49,101,110,119,139,199,200,209,229,289,319,379,409,469,

%T 559,649,739,829,919,1001,1010,1019,1039,1099,1100,1109,1129,1189,

%U 1219,1279,1309,1369,1459,1549,1639,1729,1819,1909,2000,2009,2029,2089,2119,2179

%N Numbers k such that the sum of decimal digits of k and k+1 are both prime numbers, i.e., both k and k+1 are in A028834.

%H J.W.L. (Jan) Eerland, <a href="/A092595/b092595.txt">Table of n, a(n) for n = 1..10000.</a>

%e For k=4429, digitsum(k) = 4 + 4 + 2 + 9 = 19, digitsum(k+1) = 4 + 4 + 3 + 0 = 11.

%t t=Table[0, {256}]; j=1; Do[s=Apply[Plus, IntegerDigits[n]]; s1=Apply[Plus, IntegerDigits[n+1]]; If[PrimeQ[s]&&PrimeQ[s1], Print[n]; t[[j]]=n; j=j+1], {n, 1, 10000}]; t

%t DeleteCases[ParallelTable[If[PrimeQ[Total[IntegerDigits[n]]]&&PrimeQ[Total[IntegerDigits[n+1]]],n,a],{n,2,952999}],a] (* _J.W.L. (Jan) Eerland_, Dec 20 2021 *)

%o (PARI) isok(n) = isprime(sumdigits(n)) && isprime(sumdigits(n+1)); \\ _Michel Marcus_, Jul 29 2017

%Y Cf. A028834.

%K base,nonn

%O 1,1

%A _Labos Elemer_, Mar 17 2004