A213407 First occurrence of n in A213381.
2, 0, 3, 5, 4, 9, 8, 7, 12, 17, 594270126787, 21, 20, 13, 24, 29, 16, 23, 32, 19, 36, 41, 1356, 45, 38, 151, 51, 411, 994, 57, 56, 31, 60, 65, 52, 69, 71, 37, 72, 77, 490, 81, 80, 169, 84, 6125, 68, 1043, 92, 49, 99, 101, 304, 105, 104, 55, 111, 63, 73, 89, 116, 61, 120, 125, 78, 129, 188, 67, 93, 137, 97, 18349355, 140, 433
Offset: 0
Keywords
Examples
Smallest n such that A213381(n)=9 is 17, so a(9)=17.
Programs
-
C
#include
// GCC -O3 -fopenmp #include // 11 minutes #define SIZE 4096 #define STEP 0x1000000 long long first[SIZE]; int main(int argc, char **argv) { unsigned long long a, i; for (a=0; a
Formula
a(n) = smallest k>n such that (-2)^k == n (mod k+2).
Extensions
Terms a(10) onward from Max Alekseyev, Jan 31 2014