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a(n) = p mod (p mod 10) where p = prime(n).
1

%I #39 Jan 19 2023 02:05:50

%S 0,0,0,0,0,1,3,1,2,2,0,2,0,1,5,2,5,0,4,0,1,7,2,8,6,0,1,2,1,2,1,0,4,4,

%T 5,0,3,1,6,2,8,0,0,1,1,1,0,1,3,4,2,5,0,0,5,2,8,0,4,0,1,2,6,0,1,2,0,1,

%U 4,7,2,8,3,1,1,2,2,5,0,4,5,0,0,1,7,2,8,2,0,1,5,2,4,0,4,2,5,0,1,0,1,4,2,2,0

%N a(n) = p mod (p mod 10) where p = prime(n).

%C From _Robert G. Wilson v_, Feb 12 2014: (Start)

%C a(n)=0 iff p ends in 1 (A030430) or is a single-digit prime, i.e., 2, 3, 5 or 7 (n = 1, 2, 3 or 4),

%C a(n)=3 iff n is in A142087,

%C a(n)=6 iff n is in A142094,

%C a(n)=7 iff n is in A142330,

%C a(n)=8 iff n is in A142335.

%C a(n) can never be 9. (End)

%D Idea derived from "The Creation of New Mathematics: An Application of the Lakatos Heuristic," pp. 292-298 of Philip J. Davis and Reuben Hersh, The Mathematical Experience, Houghton Mifflin Co, 1982. ISBN 0-395-32131-X.

%H Harvey P. Dale, <a href="/A046804/b046804.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Fi#final">Index entries for sequences related to final digits of numbers</a>

%e prime(10) = 29, so a(10) = 29 mod 9 = 2.

%t Mod[#,Last[IntegerDigits[#]]]&/@Prime[Range[110]] (* _Harvey P. Dale_, Jan 23 2013 *)

%t Mod[#,Mod[#,10]]&/@Prime[Range[110]] (* _Harvey P. Dale_, Aug 22 2020 *)

%K nonn,base,easy

%O 1,7

%A _Enoch Haga_

%E Name edited by _Jon E. Schoenfield_, Jan 19 2023