A053067 a(n) is the concatenation of next n numbers (omit leading 0's).

1, 23, 456, 78910, 1112131415, 161718192021, 22232425262728, 2930313233343536, 373839404142434445, 46474849505152535455, 5657585960616263646566, 676869707172737475767778, 79808182838485868788899091, 9293949596979899100101102103104105, 106107108109110111112113114115116117118119120

Offset: 1

Author

Felice Russo, Feb 25 2000

Keywords

• easy
• base
• nonn

Comments

Concatenation of the integers from A000124(n-1) up to and including A000217(n). - R. J. Mathar, Aug 30 2013

The second term is a prime. When is the next prime, if there is another? - N. J. A. Sloane, Dec 16 2016

References

• Felice Russo, A set of new Smarandache functions, sequences and conjectures in number theory, American Research Press 2000.

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..200

Crossrefs

A subsequence of A035333. For primes in latter, see A052087.

See A279610 for a variant.

Programs

Mathematica

Table[FromDigits[Flatten[IntegerDigits/@Range[(n(n-1))/2+1,(n(n+1))/2]]],{n,20}] (* Harvey P. Dale, Jan 23 2016 *)

PARI

a(n) = my(s = ""); for (i=n*(n-1)/2 + 1, n*(n+1)/2, s = concat(s, Str(i));); eval(s); \\ Michel Marcus, Aug 11 2017

Python

def a(n): return int("".join(map(str, range((n-1)*n//2+1, n*(n+1)//2+1))))
print([a(n) for n in range(1, 16)]) # Michael S. Branicky, Jan 23 2021

Extensions

More terms from James Sellers, Feb 28 2000

More terms from Michel Marcus, Aug 11 2017