A069845 Number of distinct primes obtained by inserting a 4 at all possible places in n. This includes prefixing.

1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 2, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 0, 2, 0, 0, 0, 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0

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

Cf. A069842, A069843, A069844, A069846, A069847, A069848, A069849, A069850 and A069851.

Sequence in context: A278778 A356817 A285931 * A091397 A119818 A352967

Adjacent sequences: A069842 A069843 A069844 * A069846 A069847 A069848

Keyword

base,nonn

Author

Amarnath Murthy, Apr 16 2002

Extensions

Edited and extended by Robert G. Wilson v, Apr 18 2002

Status

approved