A093712 Repeatedly subtract largest prime from n until either a prime or 1 remains.

1, 2, 3, 31, 5, 51, 7, 71, 72, 73, 11, 111, 13, 131, 132, 133, 17, 171, 19, 191, 192, 193, 23, 231, 232, 233, 2331, 235, 29, 291, 31, 311, 312, 313, 3131, 315, 37, 371, 372, 373, 41, 411, 43, 431, 432, 433, 47, 471, 472, 473, 4731, 475, 53, 531, 532, 533, 5331, 535

Offset: 1

Author

Michael Joseph Halm, May 17 2004

Keywords

• easy
• nonn
• base

Comments

The representation as strings of primes is similar to the Zeckendorf expansion, A035514's strings of Fibonacci numbers.

Examples

			a(8) = 71 because 8 = 7 + 1.
		

Crossrefs

Cf. A000040, A035514.

Programs

PARI

a(n) = {lp = List(); while(n!= 1 && ! isprime(n), p = precprime(n-1); listput(lp, p); n -= p;); listput(lp, n); return (sum(i=1, #lp, 10^(#lp - i)*lp[i]));} \\ Michel Marcus, Jun 10 2013