A045532 -id:A045532 - cp's OEIS frontend

A322828 a(n) is the concatenation of n and pi(n).

10, 21, 32, 42, 53, 63, 74, 84, 94, 104, 115, 125, 136, 146, 156, 166, 177, 187, 198, 208, 218, 228, 239, 249, 259, 269, 279, 289, 2910, 3010, 3111, 3211, 3311, 3411, 3511, 3611, 3712, 3812, 3912, 4012, 4113, 4213, 4314, 4414, 4514, 4614, 4715, 4815, 4915, 5015, 5115

Offset: 1

G. L. Honaker, Jr., Dec 26 2018

			a(5) = 53 because if n=5 then pi(5)=3, therefore concatenation gives 53.

Robert Israel, Table of n, a(n) for n = 1..10000
Chris K. Caldwell and G. L. Honaker, Jr., Prime Curios! 1027569834

Cf. A000027, A000720, A045532.

a:= n-> parse(cat(n, numtheory[pi](n))):
seq(a(n), n=1..60);  # Alois P. Heinz, Dec 28 2018

a(n) = eval(concat(Str(n), Str(primepi(n)))); \\ Michel Marcus, Dec 29 2018

A139113 Concatenation of n and n-th Fibonacci number.

Original entry on oeis.org

11, 21, 32, 43, 55, 68, 713, 821, 934, 1055, 1189, 12144, 13233, 14377, 15610, 16987, 171597, 182584, 194181, 206765, 2110946, 2217711, 2328657, 2446368, 2575025, 26121393, 27196418, 28317811, 29514229, 30832040, 311346269, 322178309

Offset: 1

Omar E. Pol, Apr 09 2008

Cf. A000027, A000045, A045532, A075110, A138821, A138822, A139114.

Table[FromDigits[Join[IntegerDigits[n],IntegerDigits[Fibonacci[n]]]],{n,40}] (* Harvey P. Dale, Dec 31 2015 *)

A154966 Primes p such that the concatenation of p and prime(p) is composite.

Original entry on oeis.org

3, 5, 7, 11, 13, 19, 29, 31, 37, 43, 47, 53, 59, 67, 73, 79, 89, 97, 101, 103, 107, 109, 113, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317

Offset: 1

Juri-Stepan Gerasimov, Jan 18 2009

			The concatenation of prime 3 and the third prime, 5, is the composite 35, hence 3 is in the sequence.
The concatenation of prime 29 and the 29th prime, 109, is the composite 29109 = 3*31*313, hence 29 is in the sequence.

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Cf. A000040 (primes), A002808 (composites), A045532.

[ p: p in PrimesUpTo(320) | not IsPrime(StringToInteger(IntegerToString(p) cat IntegerToString(NthPrime(p)))) ];

Select[Prime[Range[80]],CompositeQ[FromDigits[Flatten[IntegerDigits[ {#,Prime[ #]}]]]]&] (* Harvey P. Dale, Jan 07 2016 *)

Edited and extended beyond a(6) by Klaus Brockhaus, Jan 20 2009

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A322828 a(n) is the concatenation of n and pi(n).

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A139113 Concatenation of n and n-th Fibonacci number.

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A154966 Primes p such that the concatenation of p and prime(p) is composite.

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