OFFSET
1,19
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..20000
EXAMPLE
See the example in A069842.
MATHEMATICA
Table[ Count[ PrimeQ[ Union[ FromDigits /@ Table[ Insert[ IntegerDigits[n], 4, j], {j, 1, Floor[ Log[10, n] + 2]}]]], True], {n, 1, 105}]
PROG
(PARI) A069845(n) = { my(digs=digits(n), u=#digs, nums=Set([])); for(n=1, 1+u, nums = setunion(nums, [fromdigits(vector(1+u, i, if(i<n, digs[i], if(i>n, digs[i-1], 4))))])); #select(isprime, nums); }; \\ Antti Karttunen, Aug 23 2019
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Apr 16 2002
EXTENSIONS
Edited and extended by Robert G. Wilson v, Apr 18 2002
STATUS
approved