

A220471


Number of closed simply typable lambdaterms of size n with size 0 for the variables.


1



1, 2, 9, 40, 238, 1564, 11807, 98529, 904318, 9006364, 96709332, 1110858977
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OFFSET

1,2


COMMENTS

Typable terms are terms that satisfy constraints which make them well formed.
The current computation requires one to generate all the plain lambda terms and to sieve out those that are typable. This is feasible for the 63782411 terms of size 10 but not for the 851368766 terms of size 11.


REFERENCES

Alonzo Church, A Formulation of the Simple Theory of Types, J. Symb. Log. 5(2): 5668 (1940).
Paul Tarau, On logic programming representations of lambda terms: de Bruijn indices, compression, type inference, combinatorial generation, normalization, 2015; http://www.cse.unt.edu/~tarau/research/2015/dbx.pdf
P. Tarau, A Logic Programming Playground for Lambda Terms, Combinators, Types and Treebased Arithmetic Computations, arXiv preprint arXiv:1507.06944, 2015


LINKS

Table of n, a(n) for n=1..12.
Katarzyna Grygiel and Pierre Lescanne, Counting and generating lambdaterms, arXiv preprint arXiv:1210.2610, 2012
Paul Tarau, On a Uniform Representation for Combinators, Arithmetic, Lambda Terms and Types, preprint, 2015.
Paul Tarau, On Typedirected Generation of Lambda Terms, preprint, 2015.


CROSSREFS

Cf. A220894.
Sequence in context: A261047 A052846 A056844 * A213095 A238372 A002825
Adjacent sequences: A220468 A220469 A220470 * A220472 A220473 A220474


KEYWORD

nonn,more,changed


AUTHOR

Pierre Lescanne, Apr 10 2013


EXTENSIONS

a(11) and a(12) added from Tarau (arXiv:1507.06944, 2015).  N. J. A. Sloane, Jan 30 2016


STATUS

approved



