This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A301378 #42 Jun 25 2018 14:32:55 %S A301378 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89, %T A301378 97,11,13,17,19,23,37,41,47,49,59,61,67,73,77,83,89,91,101,103,107, %U A301378 109,31,43,47,49,53,59,61,71,77,83,89,91,97,101,103,113,37,41,43,47,61 %N A301378 a(n) = 10*A007605(n) - 9*A007652(n). %C A301378 Equivalently, a(n) is the sum of all but the last digit of the n-th prime, concatenated with that last digit. %C A301378 It appears that as the prime number xyzd transformed by (x+y+z)*10 +d; the larger the prime the less frequent the result is prime.... %H A301378 Shawn A. Broyles, <a href="/A301378/b301378.txt">Table of n, a(n) for n = 1..10000</a> %F A301378 Let ...xyzd represent the decimal expansion of prime(n); then a(n) = (... + x + y + z)*10 + d. %F A301378 a(n) = 10*A007605(n) - 9*A007652(n). - _Robert Israel_, Mar 25 2018 %e A301378 For p=1571 (prime), 1+5+7 = 13; 13*10 = 130; 130+1 = 131 (prime). %p A301378 map(t -> 10*convert(convert(t,base,10),`+`)-9*(t mod 10), [seq(ithprime(i),i=1..100)]); # _Robert Israel_, Mar 25 2018 %t A301378 Array[10 Total@ # - 9 Last@ # &@ IntegerDigits[Prime@ #] &, 67] (* _Michael De Vlieger_, Apr 27 2018 *) %o A301378 (PARI) a(n) = my(p=prime(n); d=p % 10); sumdigits(p-d)*10+d; \\ _Michel Marcus_, Mar 23 2018 %Y A301378 Cf. A007605, A007652, A176044. %K A301378 nonn,easy,base,less %O A301378 1,1 %A A301378 _Edmund Algeo_, Mar 19 2018